Neglected knee swelling: A case report of massive synovial chondromatosis

Introduction and importance: Synovial chondromatosis (SC) is a rare condition characterized by the formation of cartilaginous loose bodies within joints, primarily arising from synovial membrane metaplasia. Misdiagnosis often occurs due to nonspecific symptoms, potentially leading to joint damage if inadequately managed.

Case presentation: A 68-year-old man, presented with persistent knee pain, swelling, and limited mobility. Imaging revealed a sizable calcific mass within the knee joint, prompting surgical intervention. Arthrotomy was performed to excise an 18 cm × 15 cm × 6.5 cm mass containing multiple fused hyaline cartilaginous nodules circumscribed by a thick rim of adipose tissue. Histological examination confirmed a diagnosis of SC. Following surgery, the patient underwent physical therapy and experienced full recovery without any recurrence.

Clinical discussion: This case underscores the challenges in managing neglected advanced SC, emphasizing the role of timely surgical intervention and postoperative care in achieving favorable outcomes. The definitive diagnosis of SC relies on histopathological examination.

Conclusions: SC, an infrequent cause of knee swelling, requires early identification to prevent joint degeneration. Although malignant transformation to synovial chondrosarcoma is rare, a vigilant approach is crucial. Recurrences or resistant cases should raise suspicion for malignant transformation.