Extraarticular form of pigmented villonodular synovitis is rare and usually presents as an extension of a primary intraarticular process. Purely extraarticular lesions are even less common. Pigmented villonodular synovitis involving the synovium around the tendoachilles has not been reported. We report a unique case in a healthy 22-year-old male who presented with a swelling around the tendoachilles for a year. It became painful following a traumatic event 4 weeks prior to consultation. Magnetic resonance imaging (MRI) revealed an extraarticular soft tissue mass moulded to the posterior surface of the calcaneum. It was excised and histology revealed pigmented villonodular synovitis.
Pigmented villonodular synovitis is a progressive synovial lesion of uncertain aetiology associated with synovial-lined tissues of the joints, tendon sheaths and bursae. The incidence was 1.8 patients per million population.
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