What Is a Cyclops Lesion in the Knee?

A cyclops lesion is a complication of an ACL reconstruction surgery where there is scar tissue that inhibits full range of motion of the knee joint.

Definition

• The cyclops lesion occurs after anterior cruciate ligament surgery when the new ligament begins to fray and bundles into a knot. The cyclops lesion is a localized form of anterior arthrofibrosis. Anterior arthrofibrosis means that there is scar tissue in the front part of the joint. It occurs in 1 to 9.8 percent of patients following ACL reconstruction. The location where the lesion occurs is near the intercondylar notch. The intercondylar notch is the central bony prominence on the tibia. It also has been described as occurring in patients who have not had surgery.

Significance

• The lesion complicates the post-operative course for the patient by inhibiting full extension of the knee due to its location. A loss of full extension of the knee has a negative effect on performance, specifically in athletes.

Treatments

• The treatment consists of surgical debridement of the lesion arthroscopically. During the debridement, the surgeon cleans up the scar tissue with instruments inserted through the arthroscopic ports.

Treatment Effectiveness

• Shelbourne et al. studied nine patients who developed cyclops lesions after ACL reconstruction. Eight patients achieved near-normal range of motion after surgery to clean up the scar tissue. The other patient was 10 degrees short of full extension. At 31-month follow-up, no patient complained of symptoms of instability. Gait normalized in all patients, and eight were able to return to athletic activity.

History

• The cyclops lesion got its name from its appearance, as it sometimes looks like the central eye of the mythical Cyclops during arthroscopy due to its venous structure.