Persistent knee effusion in a young female

A 14-year-old female with painless joint effusion in the right knee was referred to our rheumatology department from the orthopaedics department. The patient first noted right joint swelling 20 days prior to referral with no history of trauma or a change in limb function. Prior to referral, the patient received non-steroidal anti-inflammatory drugs after which the joint was aspirated for the purposes of drainage. No analysis of the aspirate was performed. On clinical examination, the right knee joint was warm, full knee flexion was limited, and palpation revealed a supra patel-lar effusion. The joint was not red and no skin changes were noted. No other systemic signs were observed. Joint aspiration revealed clear synovial fluid. Routine methylprednisolone was injected into the joint immediately after aspiration. On cytology of the synovial fluid, cell count and type were within normal limits and cultures were negative. All immunological, haema-tological and biochemical tests were within normal limits. An U/S was done two weeks later due to recurrence of symptoms and synovitis of the joint was noted. A T2/sequence MRI revealed scattered areas of low signal intensity resembling haemosiderin deposition and hyperplastic thickening of the synovium. Arthroscopy of joint synovium revealed a mixture of rusty brown and white hyperplastic villi. The biopsy showed infiltration of multinucleated giant cells confirming the diagnosis of Pigmented Villonodular Synovitis. Three months later, a similar picture was seen on the left knee. MRI, arthroscopy and synovial biopsy showed similar findings on the left knee. The lesions were treated by surgical resection with total syn-ovectomy followed by radiosynoviorthesis with yttrium 90 to cover for any unresected tissue. Commentary Pigmented villonodular synovitis (PVNS) is a rare benign proliferative disorder that affects the synovium of joints 1. The nomenclature and description of PVNS has changed over the years. Chassaignac was the first to record PVNS in 1852, and described it as a nodular lesion of the synovium, which affects the flexor tendons of the phalanges. Jaffe and colleagues made the current formal description in 1941. PVNS has an indeterminate multifactorial aetiology. Neoplastic changes, genetic anomalies involving rearrangement of genes and an inflammatory response to the synovium are all currently accepted theories 2. The symptoms that suggest PVNS vary and depend on whether the lesion occurs locally or diffusely. It most frequently presents as a painful swelling, or soft tissue mass of acute onset, which is out of proportion to the degree of discomfort. …