As total knee arthroplasties (TKA) have become the gold standard procedure for severe gonarthrosis, greater interest in postperative tibiofemoral instability has developed.

Emphasizing the correlation between evaluation of symptoms and findings, offers an opportunity to elucidate the specifics of the instability.

Mandatory is the joint gap measurement during surgery to assess the effect of specific cuts or releases of the anatomic portion of the joint gap.

By performing navigation-assisted total knee arthroplasties, we are capable of measuring the joint gap in a highly reliable way.

During the ligament balancing in navigation-assisted TKA, we performed a data collection of the joint gap in 0–30 and 90 of flexion in 100 patients.

The measurements were repeated after 10 and 20 minutes in extension.

The result offers us an opportunity to assess the interesting effect of ligament-stress relaxation in TKA and to gain more insights in the further release-necessity and choice of insert during the TKA procedure.