Tibiofemoral instability in primary total knee replacement: a review, Part 1: Basic principles and classification.

Tibiofemoral instability following total knee replacement has received little attention. However it is a cause of early and late failure and usually requires revision surgery. Several factors may be implicated including improper soft tissue balancing, flexion-extension gap mismatch and acute ligamentous injuries. Meticulous surgical technique and proper prosthetic selection at the primary procedure avoids this complication.