A Rare Visitor at the Ankle: Synovial Chondromatosis of the Lateral Malleolus

Synovial chondromatosis (SC) is a rare benign disorder characterized by synovial membrane metaplasia, leading to the formation of cartilaginous nodules. It commonly affects large joints, such as the knee and hip, but its occurrence in the lateral malleolus is exceptionally rare, with very few cases reported to date.

We report the case of a 42-year-old female who presented with progressive swelling and pain over the lateral aspect of her right ankle for several months. Clinical examination revealed localized tenderness and a palpable mass over the lateral malleolus. Radiographs demonstrated calcified bodies adjacent to the lateral malleolus. The patient underwent surgical excision of the lesion. Histopathological examination revealed cartilaginous loose bodies embedded within the synovial tissue, consistent with SC. No evidence of granuloma or malignancy was found. Post-operative recovery was uneventful, and the patient remains symptom-free at follow-up.

SC involving the lateral malleolus is an extremely rare entity that may mimic other ankle pathologies. Early recognition, imaging, and histopathological confirmation are essential to prevent progression and recurrence. This case highlights the importance of considering SC in the differential diagnosis of chronic ankle swellings.