Cyclops syndrome occurring after chronic partial rupture of the anterior cruciate ligament without surgical reconstruction.

Cyclops syndrome is one of the specific causes of loss of extension of the knee following anterior cruciate ligament (ACL) reconstruction. This syndrome is manifest by progressive loss of knee extension associated with pain and audible clunk at terminal extension caused by a pedunculated nodule of fibrovascular proliferative tissue usually arising from a graft. Recent published reports, however, have described Cyclops syndrome also developing after a partial ACL rupture without surgical reconstruction. In most cases, Cyclops syndrome generally occurred within 2 months after reconstruction surgery or rupture. Here we report on the case of a patient with symptoms and arthroscopic and histological findings compatible with Cyclops syndrome that developed after a chronic partial ACL rupture that occurred 23 years ago. To our knowledge, this is the first case report of Cyclops syndrome occurring after chronic partial ACL rupture.