A Missed Case of Synovial Osteochondromatosis

Synovial osteochondromatosis or synovial chondromatosis is a benign joint pathology characterized by the development of multiple cartilaginous nodules or loose bodies in the synovial membrane that typically arise in the larger joints of the body. It usually presents as joint pain and, as seen in the present case, can occasionally be missed. Diagnosis involves a combination of clinical evaluation, imaging studies, and histopathological evaluation (which is confirmatory). Treatment depends on the severity of the disease, symptoms, and the patient's social situation, and may include monitoring for asymptomatic cases, non-surgical management (pain medications and physical therapy), or surgical intervention. Surgical intervention may include arthroscopic removal of loose bodies, synovectomy, or reconstruction/replacement in severe situations. Prognosis has a direct relationship to how early the disease is diagnosed. Early intervention with appropriate management can help alleviate symptoms; however, if left unmanaged, it can lead to joint damage and osteoarthritis or very rarely, malignant transformation into chondrosarcoma. This report describes the case of a 62-year-old female with complaints of bilateral knee pain who was originally diagnosed with osteoarthritis based on clinical exam and X-rays. Two magnetic resonance imaging (MRI) scans were done three years apart, with synovial osteochondromatosis being on the differential after the second scan. A left knee major synovectomy was conducted after the second MRI reading, where rubbery masses of tissue along with loose fragments were removed. Fluid from the tissue masses was sent to culture and pathology for interpretation. Two weeks post the surgery, the patient's pain improved tremendously, with adequate ambulation independently. Histopathology came back positive for synovial osteochondromatosis. This case report highlights the importance of keeping this joint pathology on the differential when treating patients with joint pain and interpreting imaging.