Friday, September 6, 2019

My Patient Has A Cyclops Lesion!

How the cyclops lesion looks on MRI
Two to three months after her anterior cruciate ligament (ACL) reconstruction, my patient presented with pain at the front of the knee especially when trying to straighten her knee. There is sometimes an audible clunk with the  straightening.

Her quadriceps muscles were weakened and she can't straighten her knee fully. There is often mild swelling too. There is also some soreness at the back of knee in the hamstrings and calf area.

If you haven't read the heading above, would you be able to guess what problem my patient has? There is a 4 percent chance of this happening after an ACL reconstruction.

For those not familiar, a cyclops lesion is usually a localized form of arthrofibrosis (or scar tissue) in the front of the knee joint. The cyclops lesion is a stump of tissue at the front portion of the intercondylar notch, which sits above the tibial tunnel that is drilled for the graft. The cyclops lesion usually gets impinged between the tibial and femur when straightening the leg.
intercondylar notch
How does the cyclops lesion come about? One theory suggest that it may be a remnant of the previous torn ACL stump that remained after surgery. Another theory suggest it may be fibrocartilage formed after drilling the tibial tunnel or from broken graft fibres.

Femur on top of tibia
There is also some evidence to suggest that the cyclops lesion may be a result of inappropriate surgical technique during the ACL reconstruction (Delince et al, 1998). So make sure your choose your surgeon carefully.

So how do we manage the cyclops lesion for the patient? Best way to avoid getting it is to work on regaining full knee extension immediately after the operation.

Once the tell tale signs are present (in the first paragraph of this article), not much else can be done. Yes, you read correctly, there's nothing much a physiotherapist can do. From experience, no amount of pushing, joint mobilizations, exercise or injections etc will help.

The only available option is to refer the patient back to his/ her surgeon to order an MRI to rule out or confirm the cyclops lesion. If it is a cyclops lesion, the best and actually only option is to have a knee arthroscopy and remove that naughty piece of scar tissue. This has shown to have good results (Sonnery-Cottet et al, 2010), especially if aggressive straightening commences after removing the cyclops lesion.


Delince P, Descamps PY et al (1998). Different Aspects Of The Cyclops Lesion Following Anterior Cruciate Ligament Reconstruction: A Multifactorial Etiopathogenesis. Arthroscopy. 14(8): 869-876.

Sonnery-Cottet B, Lavoie F et al (2010). Clinical And Operative Characteristics Of Cyclops Syndrome After Double-bundle Anterior Cruciate Ligament Reconstruction. Arthroscopy. 26(11): 1483-1488.
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