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Curr Sports Med Rep 2022 Jun 1;21(6):205-212. Epub 2022 Jun 1.

Department of Physical Medicine and Rehabilitation, Harvard Medical School, Spaulding Rehabilitation Hospital, Charlestown, MA.

Abstract: Knee extensor mechanism tendinopathy, including patellar and quadriceps tendinopathy, is common among athletes and those involved in jumping sports. It is largely a clinical diagnosis that presents as anterior knee pain and stiffness with associated tenderness over the affected tendon. Imaging modalities, including ultrasound and/or magnetic resonance imaging, may be helpful with the diagnosis of difficult cases or in the planning of interventional procedures. Read More

J Knee Surg 2022 Apr 28;35(5):498-501. Epub 2022 Feb 28.

Department of Radiology, University of Missouri, Columbia, Missouri.

Knee dislocations, aka multiligamentous injuries, are uncommon but devastating injuries often following high-energy trauma. Tears of the major knee stabilizers are well documented; however, injuries of the knee extensor mechanism are less commonly reported. The extensor mechanism is comprised of the patella, patellar tendon, and quadriceps tendons. Read More

OTA Int 2021 Dec 3;4(4):e149. Epub 2021 Dec 3.

Department of Orthopedic Surgery, University of Wisconsin - Madison, Madison, WI.

Objectives: We sought to determine the prevalence of intra-articular findings at the time of extensor mechanism injury that required subsequent surgical intervention.

Design: Retrospective cohort study.

Setting: Level 1 academic trauma center. Read More

Knee Surg Sports Traumatol Arthrosc 2022 Jul 1;30(7):2342-2351. Epub 2021 Dec 1.

Department of Orthopaedic Surgery, Western Health, 160 Gordon Street, Footscray, VIC, 3011, Australia.

Purpose: Patellar dislocation is associated with a range of anatomical abnormalities affecting the trochlea, extensor mechanism and the tibia. The relationship between patellofemoral instability and rotational abnormalities of the posterior condyles, trochlear groove and proximal tibia has not been adequately determined. This study aimed to identify the frequency and severity of anatomical risk factors to determine their relative contribution to patellofemoral instability. Read More

Case Rep Orthop 2021 15;2021:6686487. Epub 2021 Jul 15.

Service of Pediatric Orthopedics, Children's Hospital of Geneva, University Hospitals of Geneva, Switzerland.

Distal patellar tendon avulsions are rare injuries in healthy individuals, and to date, no case affecting skeletally mature teenagers and adolescents has been reported. In the majority of cases, distal patellar tendon avulsions are associated with severe intra-articular knee lesions, signifying a high-energy trauma. We present the case of a 15. Read More

Am J Sports Med 2021 03;49(3):706-712

Division of Orthopaedic Surgery, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.

Background: Identifying risk factors for recurrent patellar dislocation after a primary dislocation may help guide initial treatment. Magnetic resonance imaging (MRI) measurements relating the alignment of the extensor mechanism to trochlear morphology have been shown to distinguish patients with dislocations from controls, but their usefulness in predicting the risk of a second dislocation is not known.

Purpose: To identify the association of novel MRI measures of patellar containment with recurrent instability in pediatric patients presenting with a first-time patellar dislocation. Read More

Acta Orthop Traumatol Turc 2020 Sep;54(5):507-510

Department of Anatomy, Ankara University, School of Medicine, Ankara, Turkey.

Objective: This study aimed to evaluate the thickness of the remaining patellar bone stock following extra-articular knee resection (EKR) preserving the extensor mechanism in human cadaveric knee joints.

Methods: A total of 14 human cadaveric knee joints (8 men and 2 women) were dissected, and the patellar thickness from the joint capsule insertion to the anterior cortex of the patella was measured using an electronic caliper. The mean age of the cadavers was 37 years (range=28-50). Read More

AJR Am J Roentgenol 2021 06 5;216(6):1614-1625. Epub 2020 Aug 5.

Department of Radiology, Lucas Center for Imaging, Stanford University, 1201 Welch Rd, PS 055B, Stanford, CA 94305.

Potential approaches for abbreviated knee MRI, including prospective acceleration with deep learning, have achieved limited clinical implementation. The objective of this study was to evaluate the interreader agreement between conventional knee MRI and a 5-minute 3D quantitative double-echo steady-state (qDESS) sequence with automatic T2 mapping and deep learning super-resolutionaugmentation and to compare the diagnostic performance of the two methods regarding findings from arthroscopic surgery. Fifty-one patients with knee pain underwent knee MRI that included an additional 3D qDESS sequence with automatic T2 mapping. Read More

Medicine (Baltimore) 2019 Jun;98(24):e16011

Orthopaedic Medical Center, The Second Hospital of Jilin University, Changchun, China.

Rationale: Upper pole sleeve fractures of the patella are rare in adolescents; however, they are serious injuries that require early diagnosis and treatment.

Patient Concerns: We present a rare case of a 15-year-old girl who suffered a sleeve fracture at the superior pole of the right patella. The patient had a history of dislocation of the patella 2 weeks ago. Read More

J Orthop Case Rep 2018 May-Jun;8(3):18-22

Department of Orthopaedic Surgery, NYU Langone Medical Center, Hospital for Joint Diseases, New York, USA.

Introduction: Isolated tibial tubercle fractures or patellar tendon ruptures are common injuries in adolescents. However, combined tubercle fractures with patellar tendon ruptures are rare, and hence, there are no definitive methods of surgical fixation or post-operative protocols.

Case Report: A 13-year-old healthy girl sustained an extensor mechanism injury after the left knee hyperflexion during a fall from skateboarding. Read More

Am J Sports Med 2018 12 14;46(14):3400-3406. Epub 2018 Nov 14.

Division of Orthopaedics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.

Background: Abnormalities in the trochlea-patella-tibia relationship have been shown to be risk factors for recurrent patellofemoral instability, although no current measurements quantify patellar containment in the trochlea. Standard measurements, such as tibial tubercle-trochlear groove (TT-TG) distance, do not account for the containment of the patella by the trochlea. Our goal was to develop a measurement to assess how well the trochlea contained the extensor mechanism. Read More

Z Orthop Unfall 2018 Oct 5;156(5):593-607. Epub 2018 Oct 5.

Ruptures of the extensor mechanism of the knee joint are rare but disabling injuries. Injuries occur on the basis of degeneration or acute trauma. The understanding of anatomy and biomechanical function plays an essential role for choosing the right diagnostic methods and initiating successful treatment. Read More

Am J Orthop (Belle Mead NJ) 2018 Aug;47(8)

Tripler Army Medical Center, Honolulu, HI.

The purpose of this study is to determine the prevalence of potential graft-influencing pathologies of the extensor mechanism of the knee in patients presenting with a primary anterior cruciate ligament (ACL) rupture. We performed a retrospective review of the plain radiographs and magnetic resonance imaging (MRI) of all active-duty patients presenting with a primary ACL rupture at our institution between July 2006 and February 2009. Imaging was reviewed to determine the presence of a multipartite patella, unresolved Osgood-Schlatter's disease, and/or radiographic evidence suggestive of patella tendinopathy. Read More

Am J Orthop (Belle Mead NJ) 2018 Apr;47(4)

American Knee Institute, Hinsdale Orthopaedic Associates, Westmont, IL.

Blunt trauma to the anterior knee typically results in a contusion or fracture of the patella. Additionally, injury to the extensor mechanism may come from a partial or full disruption of the patellar or quadriceps tendon. A professional baseball player suffered an injury to his knee after he collided with an outfield wall. Read More

BMJ Case Rep 2018 Feb 7;2018. Epub 2018 Feb 7.

Pathology and Laboratory Medicine, King Fahad Specialist Hospital, Dammam, Saudi Arabia.

A young patient presented with a progressive right knee pain and swelling that was worse on ambulation. Following appropriate investigations, he was confirmed having Ewing's sarcoma of the right patella. Two cycles of chemotherapy were initiated before he sustained a fall and a resultant pathological patellar fracture. Read More

J Knee Surg 2018 Feb 4;31(2):141-154. Epub 2018 Jan 4.

Department of Radiology, Massachusetts General Hospital, Boston, Massachusetts.

The tendons of the knee play a critical role in the motion and stability of the knee. Knee pain, a common clinical complaint, can frequently be attributed to pathology of these structures. While the cornerstones of the radiological evaluation of the knee are radiography and magnetic resonance imaging, ultrasound can also play an important diagnostic role and can be useful for guided interventional procedures. Read More

Sports Med Arthrosc Rev 2017 Dec;25(4):227-236

Departments of *Orthopaedic Surgery §Radiology, University of Minnesota †University of Minnesota Medical School, Minneapolis ‡Department of Radiology, Mayo Clinic, Rochester, MN.

The patellofemoral joint is an articulation between the patella and the femoral trochlea, which serves to increase the lever arm of the extensor mechanism. The stability of the patella within the trochlear groove is supported statically by the bony confines of the groove itself, as well as the medial patellofemoral ligament, and dynamically by the vastus musculature. Pathologic changes seen on magnetic resonance imaging (MRI) are frequently well correlated with findings found by arthroscopy at the time of surgery. Read More

Oper Orthop Traumatol 2017 Dec 25;29(6):509-519. Epub 2017 Oct 25.

Chirurgisch-Traumatologisches Zentrum, Asklepios Klinik St. Georg, Lohmühlenstraße 5, 20099, Hamburg, Deutschland.

Objective: Anatomic reconstruction of the retropatellar articular surface and repair of the extensor mechanism of the knee joint. The osteosynthesis should allow immediate mobilization as part of an early functional postoperative rehabilitation protocol.

Indications: Displaced fractures of the patella, especially multifragment and comminuted fractures with a retropatellar incongruity or dislocation of >2 mm. Read More

J Orthop Case Rep 2017 May-Jun;7(3):5-8

Department of Orthopaedics, St. John's Medical College Hospital, Bengaluru, Karnataka, India.

Introduction: Acute concomitant rupture of both anterior cruciate ligament (ACL) and patellar tendon is a rare injury. The diagnosis of either of the injuries may be missed on clinical examination in the emergency room. A high index of suspicion is necessary when active extension is absent, and necessary investigations like ultrasound or magnetic resonance imaging (MRI) should be done to confirm the diagnosis. Read More

Injury 2017 Nov 1;48(11):2515-2521. Epub 2017 Sep 1.

Department of Orthopaedic Surgery, Texas Children's Hospital, Houston, TX, USA.

Background: Intact knee extensor mechanism is required for the normal function of the lower extremity. Patellar tendon rupture is a relatively rare injury with peak age incidence around 40 years and usually occurs midsubstance. The occurrence of pure patellar tendon rupture without bony avulsion is an extremely rare injury in the pediatric population with few cases reported in the literature with limited information regarding frequency, complications, and outcomes in children. Read More

Eklem Hastalik Cerrahisi 2017 Aug;28(2):128-31

Department of Orthopedics and Traumatology, Medical Faculty of Gazi University, 06500 Beşevler, Ankara, Turkey.

Congenital dislocation of the patella is a disorder that presents with dysfunction in extensor mechanism. Although congenital dislocation of the patella mostly occurs in children with genetic disorders, it may also occur in totally healthy children, despite rarely. In this article, we report a 16-year-old male patient who referred to our clinic with complaints of gait disturbance, frequent falls, and muscular weakness in lower extremity. Read More

J Am Acad Orthop Surg 2017 May;25(5):365-374

From the Division of Sports Medicine, Department of Orthopaedics, University of Rochester School of Medicine and Dentistry, Rochester, NY.

The knee is one of the most commonly injured joints in the body. Its superficial anatomy enables diagnosis of the injury through a thorough history and physical examination. Examination techniques for the knee described decades ago are still useful, as are more recently developed tests. Read More

Knee 2017 Mar 1;24(2):468-476. Epub 2016 Dec 1.

NYU Hospital for Joint Diseases, 301 E17th Street, New York, NY 10003, United States.

Background: Patellar tendon rupture is rare in the general population. Typically, failure occurs proximally or at the mid-substance. Distal avulsion from the tibial tubercle in adults is rare and not well described in the orthopedic literature. Read More

J Orthop Res 2017 05 12;35(5):965-973. Epub 2016 Dec 12.

McClure Musculoskeletal Research Center, Department of Orthopedics and Rehabilitation, College of Medicine, University of Vermont, Burlington, Vermont.

The complex inter-segmental forces that are developed across an extended knee by body weight and contraction of the quadriceps muscle group transmits an anteriorly directed force on the tibia that strain the anterior cruciate ligament (ACL). We hypothesized that a relationship exists between geometry of the knees extensor mechanism and the risk of sustaining a non-contact ACL injury. Geometry of the extensor mechanism was characterized using MRI scans of the knees of 88 subjects that suffered their first non-contact ACL injury and 88 matched control subjects with normal knees that were on the same team. Read More

BMC Musculoskelet Disord 2016 11 24;17(1):487. Epub 2016 Nov 24.

Norwich Radiology Academy, Norfolk and Norwich University Hospitals NHS Foundation Trust, Colney Lane, Norwich, Norfolk, NR4 7UB, UK.

Background: Fluid in the subcutaneous fat is a common finding anterior to the knee on MRI. This may be caused by chronic low-grade shearing injuries in patients who are overweight. The purpose of this study was to determine if there is a difference in the amount of subcutaneous fat around the knee between patients with these appearances and controls. Read More

J Am Acad Orthop Surg 2016 Dec;24(12):e184-e192

From the Knee Unit, Clínica Alemana, Universidad del Desarrollo, Santiago, Chile.

Patellar tendinopathy is a common cause of pain in athletes' knees. Historically, it has been related to jumping sports, such as volleyball and basketball. Repetitive jumping generates a considerable load of energy in the extensor mechanism, leading to symptoms. Read More

West J Emerg Med 2016 Nov 29;17(6):814-816. Epub 2016 Sep 29.

Stanford University School of Medicine, Department of Emergency Medicine, Stanford, California.

Traumatic injuries to the knee are common in emergency medicine. Bedside ultrasound (US) has benefits in the rapid initial detection of injuries to the patella. In addition, US can also quickly detect injuries to the entire knee extensor mechanism, including the quadriceps tendon and inferior patellar ligament, which may be difficult to diagnose with plain radiographs. Read More

Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi 2015 Oct;29(10):1204-7

Objective: To explore the effectiveness of knee extensor mechanism reconstruction in the treatment of recurrent patellar subluxation with bone anchor in adolescents.

Methods: Between January 2010 and December 2013, 20 patients with patellar subluxation were treated by knee extensor mechanism reconstruction with bone anchor. There were 11 males and 9 females, aged from 12 to 17 years (mean, 15. Read More

Arthroscopy 2016 Jan;32(1):69-70

The MRI tibial tubercle-trochlear groove distance is statistically significantly higher in adolescent and young adults with noncontact anterior cruciate ligament (ACL) tears compared with those without tears. The authors use lateral thinking to assess this marker for extensor mechanism alignment as a potential risk factor for ACL tear. Yet the approximate 2 mm increase seen in those with ACL tears portends unproven clinical significance. Read More

Radiographics 2015 Sep-Oct;35(5):1483-501. Epub 2015 Aug 21.

From the Department of Radiology and Imaging, Hospital for Special Surgery, 535 E 70th St, New York, NY 10021.

Primary total knee arthroplasty is a highly effective treatment that relieves pain and improves joint function in a large percentage of patients. Despite an initially satisfactory surgical outcome, pain, dysfunction, and implant failure can occur over time. Identifying the etiology of complications is vital for appropriate management and proper timing of revision. Read More