The history, examination, MRI, and arthroscopic intra-articular image are most consistent with a diagnosis of pigmented villonodular synovitis. PVNS is a benign condition which can predispose patients to early arthritis. It should be noted that the MRI shows nodular findings in both the anterior and posterior portions of the knee. Arthroscopic image shows the deep red fronds classic for PVNS secondary to hemosiderin deposition in the synovium. These findings are specifically reviewed in the article by Bhimani et al where they focus on the history, presentation, imaging appearance, and treatment modalities for PVNS and focus on the MRI appearance of these lesions.
Treatment for symptomatic PVNS includes synovectomy. Often this can be accomplished arthroscopically in the anterior portion of the knee, but the synovial nodules in the posterior knee often require a formal posterior arthrotomy to remove.
True intra-articular malignancies are quite rare, and despite the misnomer, synovial sarcoma is NOT an inter-articular process. Rather, synovial sarcoma tends to occur around, but not within, joint. While rheumatoid nodules, synovial chondromatosis, and lipoma arborescens are all frequent intra-articular lesions, PVNS is the most likely diagnosis based on the MRI and arthrotomy image.
DePonti et al report their 10 year experience with arthroscopic treatment of PVNS of the knee. They found that localized PVNS responded well to lesional excision but that diffuse PVNS required an extended synovectomy to accomplish stable local control of the lesion.
Chin et al report their results on 40 patients with diffuse PVNS. They divided their treatment into surgery alone, surgery and intra-articular radiation, and surgery with external beam radiation. They found the knee scores and range of motion improved post-operatively in all groups, and there was suggestion that intra-articular adjuvant radiation improved the rates of local control.
De Ponti A, Sansone V, Malcherè M. Result of arthroscopic treatment of pigmented villonodular synovitis of the knee. Arthroscopy. 2003 Jul-Aug;19(6):602-7. Review.
PMID:12861198 (Link to Abstract)
Chin KR, Barr SJ, Winalski C, Zurakowski D, Brick GW. Treatment of advanced primary and recurrent diffuse pigmented villonodular synovitis of the knee. J Bone Joint Surg Am. 2002 Dec;84-A(12):2192-202.
PMID:12473708 (Link to Abstract)
Bhimani MA, Wenz JF, Frassica FJ. Pigmented villonodular synovitis: keys to early diagnosis. Clin Orthop Relat Res. 2001 May;(386):197-202.
PMID:11347835 (Link to Abstract)