LOCALIZED ANTERIOR ARTHROFIBROSIS (CYCLOPS LESION) AFTER RECONSTRUCTION OF THE ANTERIOR CRUCIATE LIGAMENT - MR-IMAGING FINDINGS

OBJECTIVE. A localized form of anterior arthrofibrosis, the so-called cyclops lesion, has recently been reported to be a significant cause o f loss of knee extension after reconstruction of the anterior cruciate ligament (ACL) of the knee. The purpose of this study was to characte rize the MR appearance of this lesion. SUBJECTS AND METHODS. Five pati ents who had arthroscopic verification of a focal nodule of fibrous ti ssue in the intercondylar notch anterior to the reconstructed ACL (the cyclops lesion) and who had an MR examination after ACL reconstructio n but before repeat arthroscopy and excision of the cyclops lesion wer e included in this study. The MR images were evaluated for the presenc e of soft tissue in the intercondylar notch anterior to the reconstruc ted ACL, If present, this tissue was graded as 1, 2, or 3, depending o n its anterior extent along the femoral condyle. RESULTS. MR images of all five patients showed abnormal soft tissue with signal characteris tics consistent with fibrous tissue anterior to the reconstructed ACL in the intercondylar notch. The abnormal tissue was grade 2 or 3 in al l patients. CONCLUSION. MR imaging shows soft tissue with signal chara cteristics consistent with fibrous tissue anterior to the reconstructe d ACL in the intercondylar notch in patients with localized anterior a rthrofibrosis. Although the sensitivity and specificity of MR imaging for the cyclops lesion are yet to be determined, visualization of such fibrous tissue on MR images in a patient with clinical symptoms sugge stive of localized anterior arthrofibrosis may be helpful in confirmin g the diagnosis.