119 Pigmented Villonodular Synovitis

Pigmented Villonodular Synovitis

Anthony G. Ryan, Nizar Al-Nakshabandi, and Peter L. Munk

A 37-year-old man presented with discomfort and swelling of the right knee that had gradually progressed over a 2- to 3-year period. This was aggravated by activity, which often produced a marked increase in swelling.

Figure 119A

Figures 119B

Figures 119C

Radiologic Findings

The anteroposterior view of the knee (Fig. 119A) shows erosions involving both the femur and the tibia centered in the region of the intercondylar notch. The erosions are well defined with slightly sclerotic borders, consistent with a slowly enlarging soft-tissue mass.

An MRI examination shows a large effusion distending the suprapatellar bursa (Figs. 119B, 119C). On the gradient echo image (Fig. 119B), multiple punctate foci of low signal intensity are present, consistent with areas of hemosiderin deposition. Following administration of intravenous (IV) gadolinium contrast, extensive masslike enhancement is noted (Fig. 119C).

Diagnosis

Pigmented villonodular synovitis (PVNS).

Differential Diagnosis

Rheumatoid arthritis
Indolent infection
Synovial sarcoma
Hemophilia
Lipoma arborescens

Other hemosiderin-containing lesions include

Hematoma
Hemangioma

Discussion

Background

PVNS is a rare benign proliferative diffuse intra-articular growth of the synovium of obscure etiology, first described in 1941 and representing part of a disease spectrum that includes a localized form (giant cell tumor of the tendon sheath [GCTTS]). The more common (75 to 85%) of the two entities, GCTTS differs from PVNS in location, as it is classically extra-articular, located around the tendon sheaths of the hand, and usually measures < 2 cm in size.

Etiology

Although some debate persists regarding the etiology of the condition, in its diffuse form, it is widely held to be neoplastic, as evinced by the presence of mononuclear clonality and rare reported cases of metastases. Alternative etiologies suggested include an inflammatory process of unknown cause and an abnormality of local lipid metabolism. The localized form is held by some to be a local granulomatous reaction; however, a causative agent has not been identified.