Primary Synovial Chondromatosis of the Ankle: A Rare Cause of Chronic Mechanical Pain and Diagnostic Challenge – A Case Report

Abstract

Primary synovial chondromatosis is a rare benign monoarticular disorder characterized by cartilaginous metaplasia of the synovium with formation of multiple intra-articular nodules and loose bodies. Although the knee and hip are most commonly involved, ankle localization remains exceptional and may lead to delayed diagnosis because of nonspecific clinical manifestations.

We report the case of a 36-year-old woman presenting with a one-year history of progressive mechanical pain of the right ankle without restriction of motion. Clinical examination revealed mild ankle swelling, tenderness over the medial and lateral malleoli, a positive anterior drawer test, and signs of anterior impingement. Laboratory investigations were unremarkable. Plain radiographs demonstrated multiple calcified loose bodies around the tibiotalar joint associated with mild osseous erosions. Magnetic resonance imaging (MRI) revealed diffuse synovial thickening with numerous intra-articular nodules extending into the tibiotalar joint, distal tibiofibular recess, subtalar joint, and lateral malleolar region. The nodules showed low signal intensity on T1-weighted images, predominantly high signal intensity on proton density fat-suppressed sequences, and punctate signal voids corresponding to mineralized foci.

The patient underwent open synovectomy with complete removal of the loose bodies. Histopathological examination confirmed primary synovial chondromatosis. Postoperative recovery was uneventful, with favorable clinical evolution.

This case highlights the importance of considering primary synovial chondromatosis in the differential diagnosis of chronic ankle pain. MRI plays a pivotal role in identifying non-mineralized nodules, assessing disease extent, guiding surgical management, and differentiating this entity from other proliferative synovial disorders.