In a series of 38 young adults with intra-articular pigmented villonodular synovitis, the joint predominantly affected was the knee. For early diagnosis of intra-articular pigmented villonodular synovitis, a high level of suspicion is necessary for patients with complaints of persistent pain or swelling in the knee, or erosive osteoarthritis of the hip and shoulder of unknown etiology in young individuals. Arthrography of the knee was not found to be a very helpful test in the diagnosis of pigmented villonodular synovitis. Localized intra-articular pigmented villonodular synovitis should be treated by local excision. Diffuse intra-articular pigmented villonodular synovitis of the knee should be treated by extensive synovectomy followed by manipulation under general anesthesia two to three weeks postsurgery. Intra-articular pigmented villonodular synovitis of the shoulder and hip should be treated by extensive synovectomy or by total joint arthroplasty in cases with marked bone destruction and cyst formation.