Magnetic Resonance Imaging of Cyclops Lesion in Patients With Non-reconstructed Anterior Cruciate Ligament

Introduction The term cyclops lesion refers to localized anterior fibrosis, which is the abnormal proliferation of fibrous tissue in a joint that develops in the anterior aspect of the intercondylar notch. It is a known cause of extension loss of the knee after anterior cruciate ligament (ACL) reconstruction; however, it can be found in patients who have not undergone any surgical repair of the ACL. The term "cyclops lesion" was given based on the arthroscopic appearance of the fibrous nodule and vessels that resemble an eye. The purpose of this study is to highlight the existence of cyclops lesions in non-operated knees. Methods We conducted a study on 10 patients who were subjected to an MRI knee in a Siemens Magnetom Vida 3 Tesla (Erlangen, Germany) machine. We retrospectively analyzed all 10 cases in our institution from July 2021 to March 2022. These subjects had a previous history of trauma, and they presented with complaints of pain and difficulty in knee extension but no history of previous ligament repair. All patients underwent an MRI examination. When a cyclops lesion was revealed on MR imaging, the signal-intensity characteristics, location, and size were documented. Results There were a total of 10 patients included in the study, of whom eight were males and two were females. The most common clinical presentation in all our cases was difficulty in the extension of the knee, while there was associated instability and difficulty in walking in some patients. There was a demonstrable cyclops lesion near the tibial attachment of ACL in eight (80%) patients, whereas it was found to be located just lateral to the anterior intercondylar notch in the rest of the two (20%) patients. Conclusion MRI is an effective tool to evaluate unexplained pain, functional limitations, and limited range of motion in patients with suspected arthrofibrosis. MRI also helps determine the extent of fibrosis involvement and excludes other complications that may have a similar clinical picture.