A cyclops lesion is a bunched up area of scar tissue in the notch of the femur, usually seen as a complication of anterior cruciate ligament reconstruction.
A cyclops lesion filling the notch of the femur anterior to the reconstructed anterior cruciate ligament (ACL).
The original cyclops of mythology was a one-eyed monster.
Extension deficit as a result of a cyclops lesion
The bunched up tissue causes problems with achieving full extension. There may be a complete inability to achieve full extension, or it may be possible with an uncomfortable clunk.
Case Series: Cyclops lesion - extension loss after ACL reconstruction. Dhanda S, Sanghvi D and Pardiwala D. Indian J Radiol Imaging. 2010 Aug; 20(3): 208–210.
The cyclops lesion after bicruciate-retaining total knee replacement. Klaassen MA and Aikins JL. Arthroplast Today. 2017 Dec; 3(4): 242–246.