Giant intraarticular loose bodies of the knee. Cases demonstrate spectrum of the lesion.

Synovial chondromatosis is a well-known, well-described clinical and histopathologic entity. Occasionally, loose bodies in the knee joint can continue to grow and become large enough to impinge on joint motion. Extremely large synovial chondromata are relatively rare in the knee joint and have only been described in singular case reports in the orthopaedic literature. We describe two cases representing the spectrum of this disease process occurring in the popliteal fossa, simulating bony and/or soft tissue neoplasm. Case 1 demonstrates a large ossified chondroma, while Case 2 demonstrates a large chondroma without much calcification and with no ossification present. Because of the rarity of these lesions, preoperative staging studies, including CT scan, bone scan, and angiography, are usually warranted to help in the preoperative planning. Open biopsy with adequate tissue sampling is necessary to make an accurate histopathologic diagnosis. Once diagnosis is made, local excision for removal of the mechanical block to motion results in "cure"; local recurrence has not been noted.