Soft tissue management is a critical factor in total knee arthroplasty especially in valgus knees. The stepwise release has been based upon surgeon’s experience until now. Computer assisted surgery gained increasing scientific interest in recent times and allows the intraoperative measurement of leg axis and gap size in extension and flexion.

We therefore aimed to analyse the effect of the sequential lateral soft tissue release and the resulting change in the a.p. limb axis on the one hand and the tibiofemoral gaps on the other hand as well in extension as in flexion in 8 cadaveric knees. Measurements were obtained using a CT-free navigation system.

In extension the highest increase compared to the previous release step was found for the first (iliotibial band, p=0.002), second (popliteus muscle, p=0.0003), third (LCL, 0.007) and the sixth (entire PCL, p=0.001) release step. In 90° flexion all differences of the lateral release steps were statistically significant (p< 0.004). Massive progression of the lateral gap in flexion was found after the second (popliteus muscle, p=0.004) and third (LCL, 0.007) release step.

Computer assisted surgery allows to measure the effect of each release step of the sequential lateral release sequence and helps the surgeon to asses the result better.