Patellar tendinopathy caused by a para-articular/extraskeletal osteochondroma in the lateral infrapatellar region of the knee: a case report

Patellar tendinopathy is characterized by activity-related anterior knee pain. It is most commonly related to sports activity, but has also been reported in the non-athletic population. Most injuries are caused by microtrauma, resulting in tendinitis or tendinosis. Extraskeletal paraarticular osteochondromas, which occur in the soft tissues near the joint, are rare. The infrapatellar fat pad and joint capsule are the most common sites of these tumors. Here, a case of patellar tendinitis caused by an extraskeletal paraarticular osteochondroma is reported. The symptoms included intensifying pain upon flexion and a palpable click that was located at the medial side of the mass. The patient was pain-free within 3 weeks after excision of the tumor and the clicking disappeared. To our best knowledge, no other case of patellar tendinitis caused by an extraskeletal paraarticular osteochondroma has been reported in the English literature.