Case Report: A Post-Traumatic Cyclops Lesion Arising from Posterior Cruciate Ligament Injury with Loss of Extension

Introduction: Cyclops lesions or arthrofibrotic nodules of the knee, first described by Jackson and Schaefer, occur in the anterior aspect of the intercondylar notch. Arthroscopically, they appear as head-like fibrous lesions with reddish-blue discoloration areas and consist of a pedunculated nodule of fibrovascular proliferative tissue, with or without bone or cartilaginous tissue. The cyclops lesion is a localized arthrofibrotic nodule most commonly seen following anterior cruciate ligament (ACL) reconstruction but rare on posterior cruciate ligament injuries (PCL). In this study, we present a novel case of cyclops lesion from a minor PCL injury without laxity or previous surgery. Case Presentation: A 37-year-old man visited the outpatient clinic complaining of mild knee pain, intermittent locking, and extension discomfort after minor trauma. These symptoms started 3 weeks prior, during his usual baseball activity. The magnetic resonance imaging (MRI) showed an intact ACL. Still, it had a partially injured PCL, a small suprapatellar effusion, and a cyclops lesion (2.4 × 3.4 × 2.5 cm) in the intercondylar notch of the femur, originating from the PCL. An arthroscopy confirmed and excised a cyclops lesion originating from the PCL. The microscopic findings included congested blood vessels of irregular-sized veins and hemorrhagic necrosis within the wavy ligament tissues, which confirmed its origin from the ligament tissue. After arthroscopic excision, the patient’s symptoms were relieved without laxity. Conclusions: While most of these lesions can be treated efficiently by arthroscopy, the differential diagnosis should be performed for unique cases with a lesion from minor PCL injury without laxity or previous surgery.