Extension loss secondary to femoral-sided inverted cyclops lesion after anterior cruciate ligament reconstruction.

Loss of terminal knee extension after anterior cruciate ligament (ACL) reconstruction is problematic. Formation of a fibrous nodule, known as a cyclops lesion, at the site of the ACL graft exiting from the tibial tunnel can impinge at the roof of the intercondylar notch and block terminal knee extension. This article presents a case of an inverted cyclops lesion originating from the femoral tunnel site of the ACL graft, representing a variant of the traditional cyclops lesion. The lesion was identified by clinical examination including prone heel-height difference assessment in combination with magnetic resonance imaging arthrography. The lesion was treated successfully by arthroscopic resection, with rapid resolution of the patient's painful, symptomatic extension loss.