Review Question - QID 2870

In this situation, the knee is both tight in flexion (tibial tray lift-off) and extension (unable to fully extend). Of the options listed, only resection of the proximal tibia will provide more room in both flexion and extension.

Proper sagittal plane balancing in total knee arthroplasty can help prevent post-operative stiffness and/or instability through the flexion arc. In a cruciate-retaining knee arthroplasty, balancing is potentially more complicated given the presence of the posterior cruciate ligament. If the knee is too tight in flexion, the trial tibial tray can be seen "lifting-off." If the knee is too loose in flexion, the tibial tray can be easily extracted from beneath the femur when the knee is flexed to 90 degrees. If the knee is both tight in flexion and extension, which is the case here, the correct treatment should be to resect more proximal or downsize the polyethylene.

Illustration A shows normal tibial tray seating at the time of total knee arthroplasty.

Illustration B shows tibial tray lift off with flexion. This is due to the femoral component impinging on the tibial tray posteriorly and causing lift off of the tray anteriorly.

Incorrect Answers:
Answer 1: Augmenting the distal femur will increase the amount of tightness in extension.
Answer 2: Resecting more distal femur will decrease tightness in extension, but will not change the tightness in flexion.
Answer 4: Downsizing the femoral component will only affect the flexion space, not the extension space.
Answer 5: Increasing the polyethylene thickness will increase tightness in both flexion and extension. In this case, we want to do the opposite.