Publications by authors named "Ryan L Mizner"

35 Publications

Longitudinal study of knee load avoidant movement behavior after total knee arthroplasty with recommendations for future retraining interventions.

Knee 2021 Apr 16;30:90-99. Epub 2021 Apr 16.

University of Montana, School of Physical Therapy & Rehabilitation Science, Missoula, MT, United States. Electronic address:

Background: This study aimed to evaluate clinical and biomechanical changes in self-report survey, quadriceps strength and gait analysis over 3- and 6-months post-total knee arthroplasty (TKA) and confirm the immediate effects of two forms of kinetic biofeedback on improving inter-limb biomechanics during a physically demanding decline walking task.

Methods: Thirty patients with unilateral TKA underwent testing at 3- and 6-months following surgery. All underwent self-report survey, quadriceps strength and gait analysis testing. Patients were assigned to one of two types of biofeedback [vertical ground reaction force (vGRF), knee extensor moment (KEM)].

Results: No decrease in gait asymmetry was observed in non-biofeedback trials over time (p > 0.05), despite significant improvements in self-report physical function (p < 0.01, Cohen d = 0.44), pain interference (p = 0.01, Cohen d = 0.68), numeric knee pain (p = 0.01, Cohen d = 0.74) and quadriceps strength (p = 0.01, Cohen d = 0.49) outcomes. KEM biofeedback induced significant decrease in total support moment (p = 0.05, Cohen f = 0.14) and knee extensor moment (p = 0.05, Cohen f = 0.21) asymmetry compared to using vGRF biofeedback at 6-months. vGRF biofeedback demonstrated significant decrease in hip flexion kinematic asymmetry compared to KEM biofeedback (p = 0.05, Cohen f = 0.18) at 6-months.

Conclusion: Gait compensation remained similar from 3- to 6-months during a task requiring greater knee demand compared to overground walking post-TKA, despite improvements in self-report survey and quadriceps strength. Single session gait symmetry training at 6-month supports findings at 3-month testing that motor learning is possible. KEM biofeedback is more effective at immediately improving joint kinetic loading compared to vGRF biofeedback post-TKA.
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http://dx.doi.org/10.1016/j.knee.2021.03.014DOI Listing
April 2021

Patient perspectives of ankle-foot orthoses for walking ability in peripheral artery disease: A qualitative study.

J Vasc Nurs 2020 Sep 10;38(3):100-107. Epub 2020 Aug 10.

School of Physical Therapy and Rehabilitation Science, College of Health Professions and Biomedical Sciences, University of Montana, Missoula, Montana.

Calf claudication associated with peripheral artery disease results in limited walking ability and diminished quality of life. Ankle-foot orthoses (AFO) have been used to mitigate calf pain during community-based walking exercise, yet little is known about patients' perspectives of this novel device. The purpose of this qualitative study was to determine the personal impact AFO had on patients who used them. Ten patients with calf claudication who previously completed a 12-week unstructured community-based walking program supplemented by AFO participated in a semi-structured recorded focus group. After data saturation was achieved, transcripts were coded and analyzed, and 2 primary themes emerged from the focus groups: 1) positive functional impact of AFO on walking ability and quality of life and 2) self-selected AFO usage patterns. Six subthemes included 1) positive ambulatory changes from using AFO, 2) sustained ambulatory improvements without AFO, 3) positive psychosocial impact, 4) optimal conditions for AFO usage, 5) optimal ambulatory surfaces when using AFO, and 6) challenges with comorbidities. The AFO were influential in decreasing claudication symptoms, improving walking capacity, and enhancing participation in meaningful daily and recreational activities. This study explores experiential knowledge of patients with calf claudication describing AFO as an effective tool to enhance unstructured walking programs. Further trials are needed to optimize device design and effectiveness in varying walking environments.
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http://dx.doi.org/10.1016/j.jvn.2020.07.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7595830PMC
September 2020

Running Biomechanics in Individuals with Anterior Cruciate Ligament Reconstruction: A Systematic Review.

Sports Med 2019 Sep;49(9):1411-1424

Centre for Interdisciplinary Research in Rehabilitation and Social Integration, Quebec City, QC, G1M 2S8, Canada.

Background: A return to running after anterior cruciate ligament reconstruction (ACL-R) is critical to the clinical success of any cutting and pivoting athlete who wishes to return to sport. Knowledge of specific alterations during running after ACL-R is required to optimise rehabilitation for improving outcomes and long-term disability.

Objective: The objective of this systematic review was to summarise kinematic, kinetic and muscle activation data during running after ACL-R and the intrinsic factors (e.g. surgical technique and strength asymmetries) affecting running biomechanics.

Methods: MEDLINE, EMBASE, SPORTDiscus and CINAHL databases were searched from inception to 10 December, 2018. The search identified studies comparing kinematic, kinetic or muscle activation data during running between the involved limb and contralateral or control limbs. Studies analysing the effect of intrinsic factors in the ACL-R group were also included. Risk of bias was assessed, qualitative and quantitative analyses performed, and levels of evidence determined.

Results: A total of 1993 papers were identified and 25 were included for analysis. Pooled analyses reported a deficit of knee flexion motion and internal knee extension moment, compared with both contralateral or control limbs, during the stance phase of running from 3 months to 5 years after ACL-R (strong evidence). Inconsistent results were found for both peak vertical ground reaction force and impact forces after ACL-R. Patellofemoral and tibiofemoral joint contact forces differed from both contralateral or control limbs up until at least 2.5 years after ACL-R and moderate evidence indicated no difference for muscle activations during moderate speed running. Quadriceps and hamstring strength asymmetries, and knee function, but not surgical techniques, were likely to be associated with both knee kinematics and kinetics during running after ACL-R.

Conclusion: After ACL-R, knee flexion motion and internal knee extension moment are the most affected variables and are consistently smaller in the injured limb during running when pooling evidence. Clinicians should be aware that these deficits do not appear to resolve with time and, thus, specific clinical interventions may be needed to reduce long-term disability.

Systematic Review Registration: Registered in PROSPERO 2017, CRD42017077130.
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http://dx.doi.org/10.1007/s40279-019-01120-xDOI Listing
September 2019

Efficacy of ankle-foot orthoses on walking ability in peripheral artery disease.

Vasc Med 2019 08 29;24(4):324-331. Epub 2019 Mar 29.

3 University of Montana, College of Health Professions and Biomedical Sciences, School of Physical Therapy and Rehabilitation Science, Missoula, MT, USA.

Calf claudication is a significant cause of walking limitation for patients with peripheral artery disease (PAD). Ankle-foot orthoses (AFO) are leg devices that can reduce the physical demands on the calf muscles during ambulation. The purpose of this study was to determine the efficacy of AFO on walking ability in patients with PAD. This was an open-label, interventional trial including 15 patients with calf claudication who were fit with AFO. Patients completed graded treadmill testing, followed by 12 weeks of unstructured community-based walking using the AFO ad libitum. Comparison of peak walking time (PWT) at baseline versus 12 weeks was the primary outcome. A secondary outcome was claudication onset time (COT) assessed during graded treadmill tests. Change in walking ability of AFO group patients was also compared to outcomes from a historical PAD control group ( = 10) who received upfront advice to walk at home. Patients in the AFO group significantly improved their walking ability from baseline to 12 weeks (mean ± SD) (PWT: 7.8 ± 5.1 to 9.3 ± 5.4 min, = 0.049; COT: 3.0 ± 2.3 to 4.8 ± 2.7 min, = 0.01). Change in PWT for AFO group patients when tested without using the devices was not significantly greater compared to historical controls (+1.4 ± 2.4 vs +0.1 ± 2.6 min, = 0.16) but it was for COT (+1.8 ± 2.5 vs -0.6 ± 2.2 min, = 0.02). This study found that AFO used during community-based walking improved the primary outcome of PWT in patients with PAD. Further, using AFO delayed claudication onset, indicating patients may be able to increase their walking activity. Large-scale, randomized controlled trials are needed to further explore the use of AFO for PAD. .
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http://dx.doi.org/10.1177/1358863X19831765DOI Listing
August 2019

Preoperative quadriceps weakness preferentially predicts postoperative aberrant movement patterns during high-demand mobility following total knee arthroplasty.

Knee 2019 Jan 29;26(1):79-87. Epub 2018 Dec 29.

University of Utah, Department of Orthopaedics, 590 Wakara Way, Salt Lake City, UT 84108, USA. Electronic address:

Background: Nearly all patients with total knee arthroplasty show aberrant movement patterns during tasks requiring greater joint demand compared to matched peers. Greater movement compensation leads to increased loading onto other joints, decreased functional capacity and limited reserve for independence later in life. Understanding how preoperative predictors contribute to postoperative aberrant movement patterns is needed to make better decisions for patients considering total knee arthroplasty.

Methods: Forty-seven patients were tested preoperatively and six months following primary total knee arthroplasty. Demographic (age, sex, body mass), self-reported (knee pain, perception of physical performance, physical activity level), physical performance (quadriceps strength, lower limb power and timed stair climbing) and surgical metrics were collected as predictor variables. Three-dimensional models based on joint mechanic asymmetry during a decline walking task were collected at six months postoperatively. Decline walking is a preferred means to assess the surgical knee's contribution to limb performance during high-demand tasks. Bootstrap inclusion fraction was employed to compare the stability of each predictor variable prior to the final regression model.

Results: Preoperative quadriceps strength (β = 0.33; p = 0.04) showed a significant relationship with knee extensor angular impulse during loading phase. No other predictor variable had any meaningful relationship with aberrant movement patterns (p > 0.05).

Conclusion: Our findings highlight patients' preoperative quadriceps strength as a meaningful predictor of postoperative performance. Preoperative quadriceps strength should be addressed when considering the knee's ability to contribute to higher demanding mobility tasks following surgery.
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http://dx.doi.org/10.1016/j.knee.2018.12.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6377852PMC
January 2019

Comparison of 2 Forms of Kinetic Biofeedback on the Immediate Correction of Knee Extensor Moment Asymmetry Following Total Knee Arthroplasty During Decline Walking.

J Orthop Sports Phys Ther 2019 Feb 20;49(2):105-111. Epub 2018 Aug 20.

Background: Individuals with total knee arthroplasty (TKA) display interlimb knee extensor moment (KEM) asymmetry during level walking that is exacerbated as task demands are increased. Studies using biofeedback to correct interlimb KEM asymmetry following TKA have reported mixed results.

Objective: To compare the immediate effect of 2 forms of real-time kinetic biofeedback-vertical ground reaction force (vGRF) or KEM-on improving interlimb peak KEM symmetry during the weight-acceptance phase of decline walking in persons who have undergone TKA.

Methods: In this cross-sectional, controlled laboratory study, 30 participants (17 men; mean ± SD age, 61.9 ± 8.5 years; body mass index, 28.4 ± 3.7 kg/m) were allocated to either a vGRF or KEM real-time biofeedback group. Peak KEM interlimb asymmetry was obtained during both nonbiofeedback and biofeedback decline walking trials 3 months following TKA.

Results: Significant interlimb asymmetry in peak KEM was observed in both groups during the nonbiofeedback condition (KEM, P = .02; vGRF, P<.01). The KEM biofeedback group demonstrated an immediate improvement in peak KEM asymmetry (P = .42). No change in peak KEM asymmetry was observed in the vGRF biofeedback group (P = .01).

Conclusion: Knee extensor moment biofeedback has an immediate effect on improving peak KEM asymmetry 3 months post TKA. J Orthop Sports Phys Ther 2019;49(2):105-111. Epub 20 Aug 2018. doi:10.2519/jospt.2019.7800.
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http://dx.doi.org/10.2519/jospt.2019.7800DOI Listing
February 2019

Quadriceps weakness preferentially predicts detrimental gait compensations among common impairments after total knee arthroplasty.

J Orthop Res 2018 09 24;36(9):2355-2363. Epub 2018 Apr 24.

Department of Physical Therapy & Athletic Training, University of Utah, 520 Wakara Way, Salt Lake City, Utah 84108.

Patients with total knee arthroplasty (TKA) have large deficits in physical performance in comparison to their healthy age-matched peers. Limb asymmetry stemming from less relative load borne by the surgical limb during daily mobility is associated with diminished performance and worsens with greater mobility demands. How common targets of postoperative care, such as muscle weakness, lower limb extension power, residual knee pain, and poor balance confidence can influence asymmetrical limb loading remains unclear. Forty-six patients with unilateral TKA underwent testing of impairments and motion analysis during 10° decline walking at 3 and 6 months postoperatively. At 3 months, only quadriceps femoris strength asymmetry was found to be significantly related to both total support moment (M ) (β = 0.431; p < 0.001) and knee extensor moment (M ) (β = 0.493; p < 0.001) asymmetry. Again at 6 months, only quadriceps strength asymmetry was related to M (β = 0.432; p < 0.001) and M (β = 0.534; p < 0.001) asymmetry. Quadriceps strength significantly improved over time in both limbs, however, deficits between limbs remained. Persistent quadriceps weakness is a key factor associated with walking compensation patterns that are limiting the capacity for greater physical performance of patients with TKA. The pronounced asymmetry in limb and knee loading at 3 months remains unchanged until at least 6 months after surgery, and its association with quadriceps strength asymmetry does not substantially change over time. While other factors may also prompt gait compensations, emphasis on improved quadriceps strength should be a focus of efforts to resolve gait compensations and enhance physical performance outcomes. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2355-2363, 2018.
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http://dx.doi.org/10.1002/jor.23894DOI Listing
September 2018

Clinical Efficacy of Jump Training Augmented With Body Weight Support After ACL Reconstruction: A Randomized Controlled Trial.

Am J Sports Med 2018 06 20;46(7):1650-1660. Epub 2018 Mar 20.

School of Physical Therapy and Rehabilitation Science, University of Montana, Missoula, Montana, USA.

Background: Limited knee flexion and increased muscle co-contraction during jump landing are believed to diminish outcomes after anterior cruciate ligament (ACL) reconstruction. The efficacy of jump training to improve patients' mechanical and neuromuscular deficits is understudied.

Hypothesis: Jump training will improve functional, mechanical, and neuromuscular outcomes and higher repetition training augmented by body weight support will result in better retention of gains.

Study Design: Randomized controlled trial; Level of evidence, 1.

Methods: Thirty athletes (18 months after surgery) were screened, and 19 with mechanical deficits and limited clinical outcomes were enrolled in the trial. Testing included the International Knee Documentation Committee (IKDC) questionnaire, leg landing mechanics via motion analysis, knee joint effusion using a stroke test, and a surface electromyography-generated co-contraction index during a single-legged landing. Participants were randomly assigned to 1 of 2 groups: jump training with normal body weight (JTBW) and high-repetition jump training with body weight support (JTBWS). Knee effusion grading throughout training was used to assess joint tolerance. Changes in outcomes over time were analyzed with mixed-effects modeling. Immediate outcomes were compared with retention testing at 8 weeks after training by use of 2-way analyses of variance with effects of time and group.

Results: Significant effects of time were found during the training phase for all outcome measures, but no effects of group or sex were found. IKDC score (pooled; mean ± SD) increased from 76 ± 12 to 87 ± 8 ( P < .001). Knee flexion during single-legged landing increased from 57° ± 11° to 73° ± 9° ( P < .001). Average co-contraction index decreased from 37 ± 15 to 19 ± 6 ( P < .001). All measures were retained over the retention period in both groups. The relative risk of knee effusion of the JTBW group versus the JTBWS group was 4.2 (95% CI, 2.25-7.71; P < .001).

Conclusion: Jump training mitigated some risk factors for second injury and osteoarthritis in patients after ACL reconstruction. Training made lasting improvements in physical function measures as well as mechanical and neuromuscular coordination deficits. Higher repetitions used with body weight support did not improve retention but substantially reduced risk for effusion.

Clinical Relevance: Jump training is an efficacious intervention for athletes with poor outcomes after ACL reconstruction, and training with body weight support lessens the risk for excessive joint stress during practice. Registration: NCT02148172 ( ClinicalTrials.gov identifier).
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http://dx.doi.org/10.1177/0363546518759052DOI Listing
June 2018

Visual knee-kinetic biofeedback technique normalizes gait abnormalities during high-demand mobility after total knee arthroplasty.

Knee 2018 Jan 2;25(1):73-82. Epub 2018 Jan 2.

University of Utah, Department of Orthopaedics, Salt Lake City, UT, United States. Electronic address:

Background: Abnormal knee mechanics frequently follow total knee arthroplasty (TKA) surgery with these deficits amplifying as task demands increase. Knee-kinetic biofeedback could provide a means of attenuating gait abnormalities. The purposes of this study were as follows: (1) to describe the gait characteristic differences between patients with TKA and non-TKA adults during level (low-demand) and decline (high-demand) walking; and (2) where differences existed, to determine the impact of knee-kinetic biofeedback on normalizing these abnormalities.

Methods: Twenty participants six months following a primary TKA and 15 non-TKA peers underwent gait analysis testing during level and decline walking. Knee-kinetic biofeedback was implemented to patients with TKA to correct abnormal gait characteristics if observed.

Results: Patients with TKA had lower knee extensor angular impulse (p<0.001), vGRF (p=0.001) and knee flexion motion (p=0.005) compared to the non-TKA group during decline walking without biofeedback. Patients with TKA normalized their knee extensor angular impulse (p=0.991) and peak vGRF (p=0.299) during decline walking when exposed to biofeedback. No between-group differences were observed during level walking. Groups were similar in age, gender, body mass index, physical activity level, pain interference and depression scores (p>0.05).

Conclusion: Patients with TKA demonstrate abnormal gait characteristics during a high-demand walking task when compared to non-TKA peers. Our findings indicate that knee-kinetic biofeedback can induce immediate improvements in gait characteristics during a high-demand walking task. There may be a potential role for the use of visual knee-kinetic biofeedback techniques to improve gait abnormalities during high-demand tasks following TKA.
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http://dx.doi.org/10.1016/j.knee.2017.11.010DOI Listing
January 2018

Joint mechanical asymmetries during low- and high-demand mobility tasks: Comparison between total knee arthroplasty and healthy-matched peers.

Gait Posture 2018 02 21;60:104-110. Epub 2017 Nov 21.

University of Utah, Department of Orthopaedics, Salt Lake City, UT, United States; University of Utah, Department of Physical Therapy & Athletic Training, Salt Lake City, UT, United States.

Chronic inter-limb joint mechanical asymmetry has been reported following total knee arthroplasty (TKA) during low-demand mobility tasks such as level walking. However, no study has compared the inter-limb asymmetry during a high-demand mobility task such as decline walking. The objective of this cross-sectional study was to compare inter-limb asymmetry differences during both level and decline walking tasks at six months following TKA compared to asymmetry present in an age, gender, body mass index and activity level matched healthy cohort. Kinetic and kinematic gait analysis was conducted on 42 patients with TKA and 15 healthy-matched peers. Our inter-limb asymmetry results demonstrated significantly (p<0.05) greater combined limb support moment (M) (mean differences [MD]=0.17; 95% CI=0.07, 0.22), knee extensor moment (M) (MD=0.05; 95% CI=0.02, 0.09) and vertical ground reaction force (vGRF) (MD=0.03; 95% CI=0.01, 0.08) differences during decline walking compared to level walking in patients with TKA. Greater M (MD=0.24; 95% CI=0.13, 0.35), M (MD=0.08; 95% CI=0.03, 0.18), vGRF (MD=0.04; 95% CI=0.01, 0.08) and knee joint angle (MD=2.4; 95% CI=0.37, 3.80) differences were present in patients with TKA compared to healthy-matched peers during decline walking. Greater M (MD=0.13; 95% CI=0.05, 0.20) and plantarflexor moment (MD=0.06; 95% CI=0.04, 0.16) differences were present in patients with TKA compared to healthy-matched peers during level walking. Post-TKA inter-limb asymmetry during level walking worsens as the physical demands of the task are increased. Thus, even patients with good self-reported outcomes after TKA exhibit substantial deficits in their mobility reserves that could limit their independence and community mobility as they age.
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http://dx.doi.org/10.1016/j.gaitpost.2017.11.017DOI Listing
February 2018

HIGH REPETITION JUMP TRAINING COUPLED WITH BODY WEIGHT SUPPORT IN A PATIENT WITH KNEE PAIN AND PRIOR HISTORY OF ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION: A CASE REPORT.

Int J Sports Phys Ther 2015 Dec;10(7):1035-49

School of Physical Therapy and Rehabilitation Sciences, University of Montana, Missoula, MT USA.

Background And Purpose: Patients frequently experience long-term deficits in functional activity following anterior cruciate ligament reconstruction, and commonly present with decreased confidence and poor weight acceptance in the surgical knee. Adaptation of neuromuscular behaviors may be possible through plyometric training. Body weight support decreases intensity of landing sufficiently to allow increased training repetition. The purpose of this case report is to report the outcomes of a subject with a previous history of anterior cruciate ligament (ACL) reconstruction treated with high repetition jump training coupled with body weight support (BWS) as a primary intervention strategy.

Case Description: A 23-year old female, who had right ACL reconstruction seven years prior, presented with anterior knee pain and effusion following initiation of a running program. Following visual assessment of poor mechanics in single leg closed chain activities, landing mechanics were assessed using 3-D motion analysis of single leg landing off a 20 cm box. She then participated in an eight-week plyometric training program using a custom-designed body weight support system. The International Knee Documentation Committee Subjective Knee Form (IKDC) and the ACL-Return to Sport Index (ACL-RSI) were administered at the start and end of treatment as well as at follow-up testing.

Outcomes: The subject's IKDC and ACL-RSI scores increased with training from 68% and 43% to 90% and 84%, respectively, and were retained at follow-up testing. Peak knee and hip flexion angles during landing increased from 47 ° and 53 ° to 72 ° and 80 ° respectively. Vertical ground reaction forces in landing decreased with training from 3.8 N/kg to 3.2 N/kg. All changes were retained two months following completion of training.

Discussion: The subject experienced meaningful changes in overall function. Retention of mechanical changes suggests that her new landing strategy had become a habitual pattern. Success with high volume plyometric training is possible when using BWS. Clinical investigation into the efficacy of body weight support as a training mechanism is needed.

Level Of Evidence: Level 4 - Case Report.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4675189PMC
December 2015

The Effect of Body Weight Support on Kinetics and Kinematics of a Repetitive Plyometric Task.

J Appl Biomech 2016 Feb 23;32(1):69-77. Epub 2015 Sep 23.

School of Physical Therapy and Rehabilitation Science, University of Montana, Missoula, MT.

Though essential to athletic performance, the ability to land from a jump often remains limited following injury. While recommended, jump training is difficult to include in rehabilitation programs due to high impact forces. Body weight support (BWS) is frequently used in rehabilitation of gait following neurological and orthopedic injury, and may also allow improved rehabilitation of high-impact tasks. There is a differential effect of BWS on walking and running gaits, and the effect of BWS on movements with relatively large vertical displacement is unknown. The current study evaluates the effect of BWS on a replicable single-leg hopping task. We posited that progressive BWS would decrease limb loading while maintaining the joint kinematics of the task. Twenty-eight participants repetitively hopped on and off a box at each of four BWS levels. Peak vertical ground reaction forces decreased by 22.5% between 0% and 30% BWS (P < .001). Average hip, knee, and ankle internal moments decreased by 0.5 N·m/kg each. Slight kinematic changes across BWS levels were clinically insignificant. The high level of task specificity evidenced by consistent kinematics coupled with a similar reduction of internal moment at each joint suggests that BWS may be a useful strategy for rehabilitation of jumping tasks.
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http://dx.doi.org/10.1123/jab.2015-0077DOI Listing
February 2016

Changes in quadriceps and hamstring cocontraction following landing instruction in patients with anterior cruciate ligament reconstruction.

J Orthop Sports Phys Ther 2015 Apr 13;45(4):273-80. Epub 2015 Feb 13.

School of Physical Therapy and Rehabilitation Sciences, University of Montana, Missoula, MT.

Study Design: Pretest/posttest controlled laboratory study.

Objectives: To determine changes in the neuromuscular activation of the quadriceps and hamstrings following instructions aimed at improving knee flexion during a single-limb landing task in persons who have undergone anterior cruciate ligament reconstruction (ACLR).

Background: Clinicians advise patients who have undergone ACLR to increase knee flexion during landing tasks to improve impact attenuation. Another long-standing construct underlying such instruction involves increasing cocontraction of the hamstrings with the quadriceps to limit anterior shear of the tibia on the femur. The current study examined whether cocontraction of the knee musculature changes following instruction to increase knee flexion during landing.

Methods: Thirty-four physically active subjects with unilateral ACLR participated in a 1-time testing session. The kinetics and kinematics of single-leg landing on the surgical limb were analyzed before and after instruction to increase knee flexion and reduce the impact of landing. Vastus lateralis and biceps femoris activities were analyzed using surface electromyography and normalized to a maximal voluntary isometric contraction (MVIC). Cocontraction indices were integrated over the weight-acceptance phase of landing.

Results: Following instruction, peak knee flexion increased (preinstruction mean ± SD, 56° ± 11°; postinstruction, 77° ± 12°; P<.001) and peak vertical ground reaction forces decreased (preinstruction, 3.50 ± 0.42 body mass; postinstruction, 3.06 ± 0.44 body mass; P<.001). Cocontraction also decreased following instruction (preinstruction, 30.88% ± 17.68% MVIC; postinstruction, 23.74% ± 15.39% MVIC; P<.001). The change in cocontraction was correlated with a decrease in hamstring activity (preinstruction, 23.79% ± 12.88% MVIC; postinstruction, 19.72% ± 13.92% MVIC; r = 0.80; P<.001).

Conclusion: Landing instruction produced both a statistically and clinically significant change in landing mechanics in persons post-ACLR. Conscious improvement of the absorptive power of the surgical limb was marked by decreased hamstring activity and cocontraction during single-limb landing.
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http://dx.doi.org/10.2519/jospt.2015.5335DOI Listing
April 2015

Observational ratings of frontal plane knee position are related to the frontal plane projection angle but not the knee abduction angle during a step-down task.

J Orthop Sports Phys Ther 2014 Dec 3;44(12):973-8. Epub 2014 Nov 3.

UF Health at the Orthopaedics and Sports Medicine Institute, University of Florida, Gainesville, FL.

Study Design: Laboratory study, cross-sectional.

Objectives: To determine if the magnitude of frontal plane knee angle, as determined with a 3-D motion-capture system (knee abduction angle [KAA]) or digital video (frontal plane projection angle [FPPA]), varies among groups of individuals with different frontal plane knee position, as determined by observational ratings.

Background: Performing functional tasks with the knee positioned medial to the foot may increase the risk for knee injury. The KAA and FPPA are commonly used in research settings to determine injury risk. However, observational ratings of frontal plane knee position are easier to perform in the clinical setting. It is not clear whether observational ratings of knee position can be used as a surrogate for the KAA or FPPA.

Methods: Eighty-one female collegiate athletes performed a lateral step-down task. Participants were rated as good, fair, or poor based on observation of their knee position relative to the foot in the frontal plane and assigned to observational rating groups. Movement was concurrently recorded with a 3-D motion-capture system and a digital video camera to calculate KAA and FPPA, respectively.

Results: Knee abduction angle did not differ among participants assigned to the different observational rating groups (P = .265). In contrast, FPPA values differed between groups (P<.001), with the highest values in the poor group and the lowest values in the good group.

Conclusion: Observational ratings of frontal plane knee position relative to the foot are an appropriate clinical substitute for FPPA but not KAA. Therefore, observational ratings of medial knee position may be more suitable as a clinical screening tool when FPPA is the measure of interest.
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http://dx.doi.org/10.2519/jospt.2014.4960DOI Listing
December 2014

Muscle activation and coactivation during five-time-sit-to-stand movement in patients undergoing total knee arthroplasty.

J Electromyogr Kinesiol 2013 Dec 13;23(6):1485-93. Epub 2013 Aug 13.

Department of Mechanical and Materials Engineering, University of Denver, United States; Department of Physical Medicine and Rehabilitation, University of Colorado Anschutz Medical Campus, United States. Electronic address:

Quadriceps weakness is prevalent with knee osteoarthritis (OA) and after total knee arthroplasty (TKA). To compensate for quadriceps dysfunction, patients often alter movement strategies. Little is known about muscle coordination during sit-to-stand (concentric) and stand-to-sit (eccentric) movements in the acute postoperative period. This investigation characterized the distribution of muscle activation between the concentric and eccentric phases during a five-time-sit-to-stand (FTSTS) movement in late stage OA and one month after TKA. Patients and healthy participants performed a FTSTS while recording bilateral ground reaction forces (GRFs) and electromyography (EMG). Concentric and eccentric ensemble averages of the GRF and EMG were calculated for the concentric and eccentric phases. Coactivation indices, integrated EMG, and GRF were calculated for each limb and phase. Patients demonstrated higher eccentric coactivation than the healthy group. Postoperative loading was higher in the nonsurgical limb. Postoperative quadriceps activity was lower in the concentric phase and higher in the eccentric phase than the healthy group. Higher coactivation in the patients resulted from sustained distribution of quadriceps activity throughout the eccentric phase. This indicated an inability to coordinate muscle firing when rapidly lowering to a chair and occurred despite unloading of the surgical limb. Although these patterns may serve as a protective strategy, they may also impede recovery of muscle function after TKA.
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http://dx.doi.org/10.1016/j.jelekin.2013.06.008DOI Listing
December 2013

Association between long-term quadriceps weakness and early walking muscle co-contraction after total knee arthroplasty.

Knee 2013 Dec 23;20(6):426-31. Epub 2013 Jan 23.

University of Evansville, Department of Physical Therapy, 1800 Lincoln Ave., Evansville, IN 47722, United States. Electronic address:

Introduction: Quadriceps weakness is one of the primary post-operative impairments that persist long term for patients after total knee arthroplasty (TKA). We hypothesized that early gait muscle recruitment patterns of the quadriceps and hamstrings with diminished knee performance at 3months after surgery would be related to long-term quadriceps strength at 1year after TKA.

Methods: Twenty-one subjects who underwent primary unilateral TKA and 14 age-matched healthy controls were analyzed. At 3months after TKA, the maximum voluntary isometric contraction of the quadriceps and a comprehensive gait analysis were performed. Quadriceps strength was assessed again at 1year after surgery.

Results: Quadriceps muscle recruitment of the operated limb was greater than the non-operated limb during the loading response of gait (p=0.03), but there were no significant differences in hamstring recruitment or co-contraction between limbs (p>0.05). There were significant differences in quadriceps muscle recruitment during gait between the non-operated limbs of the TKA group and the healthy control group (p<0.05). The TKA group showed a significant inverse relationship between one year quadriceps strength and co-contraction (r=-0.543) and hamstring muscle recruitment (r=-0.480) during loading response at 3months after TKA.

Conclusions: The results revealed a reverse relationship where stronger patients tended to demonstrate lower quadriceps recruitment at 3months post-surgery that was not observed in the healthy peer group. The altered neuromuscular patterns of the quadriceps and hamstrings during gait may influence chronic quadriceps strength in individuals after TKA.

Level Of Evidence: III.
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http://dx.doi.org/10.1016/j.knee.2012.12.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3692574PMC
December 2013

The effect of lift teams on kinematics and muscle activity of the upper extremity and trunk in bricklayers.

J Orthop Sports Phys Ther 2013 Apr 14;43(4):232-41. Epub 2013 Jan 14.

Department of Physical Therapy, Eastern Washington University, Spokane, WA 99202, USA.

Study Design: Workplace-simulation study using a crossover design.

Objectives: To evaluate the effect of lift teams on trunk and upper extremity kinematics and muscle activity among bricklayers.

Background: Healthcare practitioners often instruct individuals with work-related musculoskeletal disorders in proper lifting techniques. Bricklayers are especially affected by lifting-related musculoskeletal disorders. Lift teams are a possible intervention for reducing exposure to heavy lifting.

Methods: Eighteen apprentice bricklayers constructed walls with concrete blocks alone (1 person) and in 2-person lift teams. Peak shoulder and trunk kinematics and normalized mean surface electromyography of the upper trapezius, lumbar paraspinals, and flexor forearm muscles were collected bilaterally. Differences between construction methods and rows 1, 3, and 6 of the wall were calculated with repeated-measures analyses of variance.

Results: Working in lift teams required less trunk flexion (P = .008) at row 1 but more sidebending at row 6 (P<.001) than working alone. Dominant-side lumbar paraspinal activity was lower at row 3 (P = .008) among lift-team workers. Lift-team peak shoulder flexion was lower at row 3 (P = .002), whereas abduction was higher at rows 1 (P = .007) and 6 (P<.001). Concomitantly, nondominant upper trapezius activity and flexor forearm activity were significantly higher for lift teams at row 6 (P<.001 and P = .007). Block moment arm was significantly greater for lift teams at all rows (P≤.002).

Conclusion: Working in lift teams may be a beneficial intervention for reducing trunk flexion and lumbar paraspinal activity when bricklayers work at heights between the knees and waist, but lift teams are not recommended at higher working heights.
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http://dx.doi.org/10.2519/jospt.2013.4249DOI Listing
April 2013

Comparison of 2-dimensional measurement techniques for predicting knee angle and moment during a drop vertical jump.

Clin J Sport Med 2012 May;22(3):221-7

School of Physical Therapy & Rehabilitation Science, The University of Montana, Missoula, Montana 59812, USA.

Objective: To determine the association of 2-dimensional (2D) video-based techniques and 3-dimensional (3D) motion analysis to assess potential knee injury risk factors during jump landing.

Design: Observational study.

Setting: Research laboratory.

Participants: Thirty-six female athletes in cutting and pivoting sports.

Assessment Of Risk Factors: : Athletes performed a drop vertical jump during which movement was recorded with a motion analysis system and a digital video camera positioned in the frontal plane.

Main Outcome Measures: The 2D variables were the frontal plane projection angle (FPPA), the angle formed between thigh and leg, and the knee-to-ankle separation ratio, the distance between knee joints divided by the distance between ankles. The 3D variables were knee abduction angle and external abduction moment. All variables were assessed at peak knee flexion. Linear regression assessed the relationship between the 2D and 3D variables. In addition, intraclass correlation coefficients (ICC) determined rater reliability for the 2D variables and compared the 2D measurements made from digital video with the same measurements from the motion analysis.

Results: : The knee-to-ankle separation ratio accounted for a higher variance of 3D knee abduction angle (r = 0.350) and knee abduction moment (r = 0.394) when compared with the FPPA (r = 0.145, 0.254). The digital video measures had favorable rater reliability (ICC, 0.89-0.94) and were comparable with the motion analysis system (ICC, ≥ 0.92).

Conclusions: When compared with the FPPA, the knee-to-ankle separation ratio had better association with previously cited knee injury risk factors in female athletes. The 2D measures have adequate consistency and validity to merit further clinical consideration in jump landing assessments.
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http://dx.doi.org/10.1097/JSM.0b013e31823a46ceDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3340567PMC
May 2012

Emerging perspectives related to quadriceps central activation deficits in patients with total knee arthroplasty.

Authors:
Ryan L Mizner

Exerc Sport Sci Rev 2012 Apr;40(2):61-2

School of Physical Therapy and Rehabilitation Science, University of Montana, Missoula, MT, USA.

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http://dx.doi.org/10.1097/JES.0b013e31824c44cbDOI Listing
April 2012

Measuring functional improvement after total knee arthroplasty requires both performance-based and patient-report assessments: a longitudinal analysis of outcomes.

J Arthroplasty 2011 Aug 20;26(5):728-37. Epub 2010 Sep 20.

Department of Physical Therapy, University of Delaware, 301 McKinly Laboratory, Newark, Delaware 19716, USA.

The purpose was to explore the responsiveness of both patient-report and performance-based outcome measures to determine functional changes during the acute and long-term postoperative recovery after total knee arthroplasty (TKA). One hundred patients scheduled for unilateral TKA underwent testing preoperatively and at 1 and 12 months postoperatively using the Delaware Osteoarthritis Profile. All physical performance measures decreased initially after surgery then increased in the long term; however, the perceived function did not follow the same trend, and some showed an increase immediately after surgery. Patient-report measures were variable, with no to small response early, but had excellent long-term responsiveness that was twice as large as performance measures. Patient perception fails to capture the acute functional declines after TKA and may overstate the long-term functional improvement with surgery.
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http://dx.doi.org/10.1016/j.arth.2010.06.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3008304PMC
August 2011

Invited commentary.

Authors:
Ryan L Mizner

Phys Ther 2010 Sep;90(9):1296-8

School of Physical Therapy and Rehabilitation Science, The University of Montana, Missoula, MT 59812, USA.

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http://dx.doi.org/10.2522/ptj.20100058.ic1DOI Listing
September 2010

The long-term contribution of muscle activation and muscle size to quadriceps weakness following total knee arthroplasty.

J Geriatr Phys Ther 2009 ;32(2):79-82

Department of Physical Therapy, University of Utah, Salt Lake City, UT 84108, USA.

Purpose: Many older individuals have persistent quadriceps strength impairments after a total knee arthroplasty (TKA). A combination of muscle atrophy and neuromuscular activation deficits apparently contributes to residual strength impairments. The purpose of this short report is to describe the contribution of quadriceps muscle activation and muscle volume to impaired muscle strength in older individuals an average of 21 months following a TKA.

Methods: Seventeen individuals (males: 3, females: 14; mean age: 68 yrs +/- 8.7; BMI: 33 +/- 4.8 kg/m2; number of TKA: 24; average postoperative months: 21 +/- 11.3) recruited from an orthopaedic surgeon's practice provided their written consent and participated in this study. Quadriceps strength (MVIC) and voluntary quadriceps muscle activation (QA) were measured with use of a burst-superimposition technique in which a supramaximal burst of electrical stimulation is superimposed on an MVIC. Quadriceps volume (QV) was assessed from magnetic resonance images of the quadriceps.

Results: The mean quadriceps strength was 107.3 Nm +/- 36.4 (range: 43.22 - 205.2). The mean QA (as described with a central activation ratio) was 0.97 +/- 0.04 (range: 0.83 - 1.00). The mean QV was 1093 cm3 +/- 311.80 (range: 653.66 - 1706.56). QA and QV explain 85% of the variance in quadriceps strength (R2 = .85, p < 0.001), with QV having the greatest contribution to strength (R2 = .77, p < 0.001).

Conclusions: QV is a much stronger predictor of quadriceps strength than QA in individuals more than 1 year following TKA. Activation levels contributed little to strength one year following TKA, compared to its profound contribution in the first few postoperative months. Physical therapy interventions focused on improving muscle size in this population should be considered more relevant than countermeasures addressing neuromuscular activation.
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March 2010

Impact of body mass index on functional performance after total knee arthroplasty.

J Arthroplasty 2010 Oct 30;25(7):1104-9. Epub 2009 Oct 30.

Physical Therapy Program, Department of Physical Medicine and Rehabilitation, University of Colorado Denver, Aurora, Colorado 80045, USA.

The purpose of this investigation was to determine whether functional performance and self-report outcomes are related to body mass index (BMI) after total knee arthroplasty (TKA). We hypothesized that higher BMIs would negatively affect functional performance as assessed by the timed up-and-go test, stair climbing test, 6-minute walk test, and self-report questionnaires. A total of 140 patients with BMIs ranging from 21.2 to 40.0 kg/m2 were followed over the first 6 months after unilateral TKA. Hierarchical linear regression was used to evaluate the impact of BMI on functional performance at 1, 3, and 6 months after TKA, while taking into account preoperative functional performance. There were no meaningful relationships between BMI and functional performance in the subacute (1 and 3 months) and intermediate (6-month) stages of recovery.
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http://dx.doi.org/10.1016/j.arth.2009.08.009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2891410PMC
October 2010

Improved function from progressive strengthening interventions after total knee arthroplasty: a randomized clinical trial with an imbedded prospective cohort.

Arthritis Rheum 2009 Feb;61(2):174-83

University of Delaware, Newark, DE, USA.

Objective: To determine the effectiveness of progressive quadriceps strengthening with or without neuromuscular electrical stimulation (NMES) on quadriceps strength, activation, and functional recovery after total knee arthroplasty (TKA), and to compare progressive strengthening with conventional rehabilitation.

Methods: A randomized controlled trial was conducted between July 2000 and November 2005 in an academic outpatient physical therapy clinic. Two hundred patients who had undergone primary, unilateral TKA for knee osteoarthritis were randomized to 1 of 2 interventions 4 weeks after surgery, and 41 patients eligible for enrollment who did not participate in the intervention were tested 12 months after surgery (standard of care group). All randomized patients received 6 weeks of outpatient physical therapy 2 or 3 times per week through 1 of 2 intervention protocols: an exercise group (volitional strength training) or an exercise-NMES group (volitional strength training and NMES). Treatment effects were evaluated by a burst superimposition test to assess quadriceps strength and volitional activation 3 and 12 months postoperatively. The Medical Outcomes Study Short Form 36 and Knee Outcome Survey were completed. Knee range of motion, Timed Up and Go, Stair-Climbing Test, and 6-Minute Walk were also measured.

Results: Strength, activation, and function were similar between the exercise and exercise-NMES groups at 3 and 12 months. The standard of care group was weaker and exhibited worse function at 12 months compared with both treatment groups.

Conclusion: Progressive quadriceps strengthening with or without NMES enhances clinical improvement after TKA, achieving similar short- and long-term functional recovery and approaching the functional level of healthy older adults. Conventional rehabilitation does not yield similar outcomes.
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http://dx.doi.org/10.1002/art.24167DOI Listing
February 2009

Treatment in an outpatient setting for a patient with an infected, surgical wound with hypergranulation tissue.

Int J Low Extrem Wounds 2009 Mar 30;8(1):37-44. Epub 2008 Dec 30.

Rockwood Clinic, Spokane, WA 99218, USA.

The purpose of this article is to describe a multifaceted approach to wound care in an outpatient setting for a patient with an infected, nonhealing surgical wound with hypergranulation tissue following fasciotomy for acute compartment syndrome. A 44-year-old male underwent an anterior and lateral lower extremity compartment fasciotomy and developed a persistent right anterolateral lower leg wound. Thirty-six days after fasciotomy he came to the authors' clinic after 2 failed skin grafts with an infected wound covered in hypergranulation tissue. Treatment included sharp debridement, saline irrigation, patient education, and dressing changes during 9 treatment sessions. The patient's total wound surface area decreased from 5.2 cm x 17.3 cm to 4 cm x 15 cm with increased epithelialization from approximately 40% to 85% after 29 days of treatment. This article demonstrates the positive effect of a multifaceted approach for facilitation of wound healing in a lower extremity wound following fasciotomy.
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http://dx.doi.org/10.1177/1534734608329684DOI Listing
March 2009

Muscle strength in the lower extremity does not predict postinstruction improvements in the landing patterns of female athletes.

J Orthop Sports Phys Ther 2008 Jun 10;38(6):353-61. Epub 2008 Apr 10.

Department of Physical Therapy, Eastern Washington University, Spokane, WA, USA.

Study Design: Preinstruction and postinstruction testing in a laboratory setting.

Objectives: To examine the predictive relationship between lower extremity muscle strength and the immediate postinstruction changes in landing patterns of female athletes. We hypothesized that greater strength would be associated with larger postinstruction improvements in landing patterns.

Background: Female athletes in high-demand sports may be predisposed to anterior cruciate ligament injury because of poor landing patterns. Instruction has been shown to improve landing patterns. Lower extremity muscular strength may determine the potential for instruction to alter landing patterns.

Methods And Measures: Thirty-seven female collegiate athletes in high-demand sports participated. Strength was assessed in the following muscle groups: trunk extensors and flexors, hip abductors and extensors, knee flexors and extensors, and ankle plantar flexors. Strength testing was followed by kinetic and kinematic analysis of a drop vertical jump task. Athletes then received verbal instruction on how to improve their landing technique and were retested. Landing variables of interest were force absorption time, peak vertical ground reaction force (vGRF), peak knee flexion and abduction angle, and peak external knee abduction moment. Preinstruction and postinstruction landing variables data were compared. Linear regression models were created with strength values as independent variables and landing variables as dependent variables.

Results: After instruction, athletes significantly increased their force absorption time and peak knee flexion angle, while decreasing their peak vGRF, peak knee abduction angle, and peak external knee abduction moment (P<.001). None of the regression models were statistically significant (P>.05).

Conclusions: A brief instructional session promotes short-term improvements in the landing patterns of collegiate female athletes, but muscular strength was a poor predictor of the improvements.
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http://dx.doi.org/10.2519/jospt.2008.2726DOI Listing
June 2008

Total knee arthroplasty: muscle impairments, functional limitations, and recommended rehabilitation approaches.

J Orthop Sports Phys Ther 2008 May 14;38(5):246-56. Epub 2007 Dec 14.

Department of Physical Therapy, University of Utah, Salt Lake City, UT 84108, USA.

Unlabelled: The number of total knee arthroplasty (TKA) surgeries performed each year is predicted to steadily increase. Following TKA surgery, self-reported pain and function improve, though individuals are often plagued with quadriceps muscle impairments and functional limitations. Postoperative rehabilitation approaches either are not incorporated or incompletely address the muscular and functional deficits that persist following surgery. While the reason for quadriceps weakness is not well understood in this patient population, it has been suggested that a combination of muscle atrophy and neuromuscular activation deficits contribute to residual strength impairments. Failure to adequately address the chronic muscle impairments has the potential to limit the long-term functional gains that may be possible following TKA. Postoperative rehabilitation addressing quadriceps strength should mitigate these impairments and ultimately result in improved functional outcomes. The purpose of this paper is to describe these quadriceps muscle impairments and discuss how these impairments can contribute to the related functional limitations following TKA. We will also describe the current concepts in TKA rehabilitation and provide recommendations and clinical guidelines based on the current available evidence.

Level Of Evidence: Therapy, level 5.
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http://dx.doi.org/10.2519/jospt.2008.2715DOI Listing
May 2008

Examining outcomes from total knee arthroplasty and the relationship between quadriceps strength and knee function over time.

Clin Biomech (Bristol, Avon) 2008 Mar 3;23(3):320-8. Epub 2007 Dec 3.

Department of Physical Therapy, Graduate Program in Biomechanics and Movement Sciences, Center for Biomedical Engineering Research University of Delaware, Newark, DE 19716, USA.

Background: Temporal-spatial gait parameters improve following total knee arthroplasty (TKA) but lower limb kinematics and moments fail to match those of age-matched healthy individuals. The aim of this study was to determine whether quadriceps strength, clinical measures of knee function, lower limb kinematics, and joint moments improve following arthroplasty and normalize over time.

Methods: Twelve patients underwent total knee arthroplasty were tested at 3 and 12 months following surgery. Twelve matched controls were also tested. All underwent quadriceps strength testing and gait analysis to calculate knee joint kinematics and kinetics. Function was assessed using clinical tests and self-report.

Findings: All clinical measures except for quadriceps strength significantly improved from 3 to 12 months. Gait asymmetry was observed at 3 months (lower stance times, peak knee flexion angle, range of motion and vertical ground reaction force), but ankle, knee and hip moments contributing to the total limb support moment were equivalent between legs. At 12 months, gait speed remained significantly slower than controls. Inter-limb differences in peak knee flexion angle and range of motion persisted. Greater hip and lower knee moments were evident in the operated limb, compared to the non-operated limb and controls. Quadriceps strength was positively correlated with faster times on the Time Up and Go and Stair Climbing Test and greater distances during the 6 Minute Walk test.

Interpretation: Patients who have undergone TKA demonstrate improvements in function as measured by self-report and functional performance measures. Gait becomes more symmetric and quadriceps strength becomes stronger. Some approached the values of healthy control subjects. Important differences still remain however. The larger hip extensor contribution to the total support moment may be to compensate for the diminished knee extensor contribution during level walking. Since instrumented gait analysis and functional performance measures appear to reflect different aspects of recovery following total knee replacement, both should be considered when evaluating gait and function.
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http://dx.doi.org/10.1016/j.clinbiomech.2007.10.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2293974PMC
March 2008

Altered loading during walking and sit-to-stand is affected by quadriceps weakness after total knee arthroplasty.

J Orthop Res 2005 Sep 28;23(5):1083-90. Epub 2005 Mar 28.

Department of Physical Therapy, University of Delaware, Newark, DE 19716, USA.

Purpose: Total knee arthroplasty (TKA) successfully reduces pain, but has not achieved comparable improvements in function. We hypothesized that quadriceps strength affects performance by altering loading and movement patterns during functional tasks.

Methods: Fourteen subjects with isolated, unilateral TKA were tested three months after surgery. Quadriceps strength was assessed isometrically and kinematics, kinetics, and EMG were collected during level walking and sit-to-stand (STS). Function was assessed using the timed up and go test (TUG), stair climbing test (SCT), and the 6 min walk test (6MW).

Results: Functional performance was significantly related to the quadriceps strength of both legs, but was more strongly related to the uninvolved strength (involved rho=-0.43 with TUG; -0.65 with SCT; 0.64 with 6MW) (uninvolved rho=-0.63 with TUG; -0.68 with SCT; 0.77 with 6MW). During STS, subjects shifted weight away from the operated limb (p<0.01). Quadriceps muscle activity and the extension moments at the knee and hip were smaller in the involved compared to the uninvolved (p<0.05). The amount of asymmetry in knee excursion during weight acceptance in gait, the asymmetry in weight bearing from sit-to-stand, and the uninvolved hip extension moment during STS were related to the amount of asymmetry in quadriceps strength (rho>0.56, p<0.05).

Conclusions: Quadriceps weakness in patients with TKA has a substantial impact on the movement patterns and performance of the knee during functionally important tasks.
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http://dx.doi.org/10.1016/j.orthres.2005.01.021DOI Listing
September 2005

Quadriceps strength and the time course of functional recovery after total knee arthroplasty.

J Orthop Sports Phys Ther 2005 Jul;35(7):424-36

Department of Physical Therapy, University of Delaware, Newark, DE, USA.

Study Design: Prospective study with repeated measures.

Objectives: The overall goal of this investigation was to describe the time course of recovery of impairments and function after total knee arthroplasty (TKA), as well as to provide direction for rehabilitation efforts. We hypothesized that quadriceps strength would be more strongly correlated with functional performance than knee flexion range of motion (ROM) or pain at all time periods studied before and after TKA.

Background: TKA is a very common surgery, but very little is known regarding the influence of impairments on functional limitations in this population.

Methods And Measures: Forty subjects who underwent unilateral TKA followed by rehabilitation, including 6 weeks of outpatient physical therapy, were studied. Testing occurred at 5 time periods: preoperatively, and at 1, 2, 3, and 6 months after surgery. Test measures included quadriceps strength, knee ROM, timed up-and-go test, timed stair-climbing test, bodily pain, and general health and knee function questionnaires.

Results: Subjects experienced significant worsening of knee ROM, quadriceps strength, and performance on functional tests 1 month after surgery. Quadriceps strength went through the greatest decline of all the physical measures assessed and never matched the strength of the uninvolved limb. All measures underwent significant improvements following the 1-month test. Quadriceps strength was the most highly correlated measure associated with functional performance at all testing sessions.

Conclusions: Functional measures underwent an expected decline early after TKA, but recovery was more rapid than anticipated and long-term outcomes were better than previously reported in the literature. The high correlation between quadriceps strength and functional performance suggests that improved postoperative quadriceps strengthening could be important to enhance the potential benefits of TKA.
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http://dx.doi.org/10.2519/jospt.2005.35.7.424DOI Listing
July 2005