Giant Extra-Articular Synovial Chondromatosis of the Ankle Joint – A Rare Case Report

INTRODUCTION: Synovial chondromatosis (SC) commonly involves large joints such as the knee and hip with smaller joints being less frequently involved. Extra-articular involvement is very rare, and here, we are presenting the first case of giant extra-articular SC originating from the ankle joint. CASE REPORT: A 42-year-old male presented to the outpatient department with painless swelling over the lateral malleolus for 2 years. Diagnostic imaging suggested the involvement of the synovial lining with the swelling. The mass was excised and histopathology proved the diagnosis of SC. CONCLUSION: Extra-articular involvement in SC has been mainly reported in the synovial sheath or bursae of the hand and foot, but they can involve ankle joint also. In recent times, there have been concerns about potential malignant transformation of these lesion to chondrosarcoma, diagnosing these lesions have become important.