The purpose of this study was to evaluate and describe the clinical results of complete arthroscopic synovectomy through the four arthroscopic portals in the knees affected by diffuse pigmented villonodular synovitis (DPVNS). Between 2009 and 2012, 21 patients (15 men and 6 women) with the diffuse form of PVNS of the knee were enrolled in the study after qualification. The clinical diagnosis was confirmed by magnetic resonance imaging and postsurgical pathologic examination.