Extensive Synovial Osteochondromatosis Secondary to Avascular Necrosis of the Femoral Head: A Case of Multifocal Extra-articular Involvement.

Synovial osteochondromatosis (SOC) is an uncommon benign disorder of synovial metaplasia, characterized by cartilaginous or osseous loose bodies within the joint, bursa, or tendon sheath. We report a case of a 40-year-old female who presented initially with hip pain and limitation of motion on her right side. Imaging revealed avascular necrosis (AVN) of the femoral head along with depicted early SOC. The patient had significant symptom relief with conservative management. However, at follow-up, imaging consistently demonstrated significant progression of SOC with numerous calcified loose bodies intra- and extra-articularly involving adjacent muscle groups. There were also moderate findings of secondary osteoarthritis of the hip noted. The patient was scheduled for open surgical synovectomy. This case illustrates the aggressive nature of secondary SOC within the setting of the necrotic femoral head and calls for early imaging and surgical planning within the complex arena of joint disorders.