The unstable TKA: You rock, it rolls

Virtually any of 8 modes of knee arthroplasty failure can lead to the joint giving way. Each problem should be identified and specifically corrected. True tibial–femoral instability generally results from ligament failure, often with problems of component size and position. Three modes of true tibial–femoral instability can be identified: (a) varus–valgus or coronal plane, (b) “in the plane of motion” or sagittal plane, and (c) flexion. Revision surgery is generally required for true tibial–femoral instability. Isolated soft tissue reconstructions do not address all the contributory factors and have usually been unsuccessful.