Aim of the study: to present a rare case of synovial chondromatosis involving the knee joint in a young female patient, highlighting its clinical features, diagnostic challenges, pathological findings, and management outcomes, in the context of its recent reclassification as a benign neoplasm.

Materials and methods. A 19-year-old female presented with chronic swelling and pain in the right knee for one year, with increased pain and restricted joint movement over the past two months. Clinical evaluation, fine-needle aspiration cytology, and magnetic resonance imaging were performed. The patient underwent open surgical excision with extensive synovectomy, and the excised specimen was subjected to detailed gross and histopathological analysis.

Results. Magnetic resonance imaging revealed multiple intra-articular cartilaginous nodules within the knee joint, predominantly located around the cruciate ligaments and Hoffa’s fat pad. Gross examination revealed multiple grayish-white nodules, while histopathology demonstrated lobules of hyaline cartilage lined by synovium without atypia, confirming the diagnosis of synovial chondromatosis. Postoperative recovery was uneventful with significant improvement in joint mobility. At the three-month follow-up, the patient achieved full, painless range of motion, and no recurrence was noted clinically or radiologically at six months.

Conclusions. Synovial chondromatosis is a rare benign neoplasm of the synovium that may mimic other intra-articular pathologies. Diagnosis requires a combination of clinical, radiological, and histopathological findings. Complete surgical excision with synovectomy offers excellent functional recovery and minimizes the risk of recurrence. Vigilant long-term follow-up is recommended to monitor for potential malignant transformation.