MSK
Intracapsular (osteo-)chondroma of the knee is a rare benign tumor of cartilaginous origin due to extrasynovial metaplasia, usually located within the infrapatellar fat pad.
The main differential diagnoses include:
localized tenosynovial giant cell tumor (also known as intraarticular giant cell tumor of the tendon sheath)
calcified synovial sarcomas
calcifying bursitis
primary synovial chondromatosis
periosteal chondromas