MRI findings of cyclops lesions of the knee

Abstract

Cyclops lesions develop in the anterior aspect of the intercondylar notch typically after anterior cruciate ligament (ACL) reconstruction or injury. It is a lesion consisting of fibrous tissue with or without cartilage and bony components. A cyclops lesion is one of the causes for reduced extension and, in the cases reported here, also knee pain or discomfort after ACL reconstruction. We present the MRI features, particularly the features on proton density weighted turbo spin echo (PDW TSE) and proton density weighted turbo spin echo fat saturation (PDW TSE FS) sequences of four cases of cyclops lesions, and distinguish between the MRI findings of large and small lesions. We also describe a cyclops lesion after a posterior cruciate ligament reconstruction, not described in literature before.