Noninflammatory Intraarticular Pathology

Pigmented Villonodular Synovitis

Introduction

Etiology

Pigmented villonodular synovitis (PVNS) is a benign proliferative synovial disorder that can occur in a diffuse or localized form and in both intraarticular and extraarticular locations. Although PVNS typically occurs diffusely within a joint, nodular forms exist and, when present, are commonly referred to as localized nodular synovitis. Extra-articular PVNS can involve tendon sheaths or bursae. Localized nodular synovitis of tendon sheaths is generally designated a giant cell tumor of the tendon sheath. These are most frequent in the hand (see eFig. 95-5 ).

Prevalence and Epidemiology

PVNS is a monarticular arthropathy most frequently involving the large joints of the lower extremity and mostly affecting the knee. It is seen in decreasing frequency in the hip, ankle, shoulder, and elbow. It typically affects adults 20 to 50 years of age, with no gender predilection.

Clinical Presentation

Patients complain of progressive joint pain, decreased range of motion, and recurrent effusions, sometimes hemorrhagic ( Fig. 63-1 ).

FIGURE 63–1, Pigmented villonodular synovitis (PVNS). Like synovial osteochondromatosis, PVNS should be considered whenever a young adult presents with a monarticular noninflammatory arthropathy. Similarly, the degree of erosion is inversely proportional to the joint capacity and is also related to extent/distribution of synovial proliferation. Unlike synovial osteochondromatosis, calcification is not a characteristic of PVNS.

Pathophysiology

Grossly, a tan mass of villi and folds of synovium appears reddish due to hemosiderin deposition. Histologically, brownish red or tan projections of synovium are composed of fibrous stroma with multinucleated giant cells, xanthomatous cells, and intracellular and extracellular hemosiderin. ( Figs. 63-2 and 63-3 ) Frequently, localized nodular synovitis contains less hemosiderin than its more diffuse articular counterpart (see Fig. 95-11 ).

FIGURE 63–2, Pigmented villonodular synovitis (PVNS) can be focal or diffuse; also, the amount of hemosiderin and therefore signal intensity on T2-weighted images varies. The differential for dark synovium includes PVNS, synovial osteochondromatosis, gout, hemophilia, amyloid, postoperative, and chronic arthropathy with scarring.

FIGURE 63–3, As with other arthropathies, pigmented villonodular synovitis (PVNS) can extend into contiguous compartments. STIR , Short tau inversion recovery.

Manifestations of the Disease

Joint Effusion

Radiographic

PVNS in the knee typically manifests as a nonspecific joint effusion on radiographs, although occasionally the fluid may appear dense if hemorrhagic.

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