Effect of selective lateral ligament release on stability in knee arthroplasty

The current authors evaluated a fundamental approach to balancing the lateral ligaments of the knee that begins with aligning the implants correctly in flexion and extension, proceeds to assessing stability in flexion and extension, and concludes with releasing tight structures based on their function throughout the arc of flexion. Seventeen knees from cadavers were used to evaluate stability at various degrees of flexion after total knee arthroplasty, and then stability was reevaluated after release of selected ligaments. The iliotibial band and posterior capsule were effective lateral stabilizers only in full extension. The lateral collateral ligament had a major stabilizing effect throughout the arc from 0degrees to 90degrees flexion. The iliotibial band and poplitens tendon and posterolateral corner capsule had little effect when the other ligaments were intact. When tested in the absence of the other lateral ligaments, the popliteus tendon and posterolateral corner capsule had significant stabilizing effects throughout the flexion arc. The popliteus tendon exerted its effect mostly from 60degrees to 90degrees flexion. The posterolateral corner capsule was effective mostly at 0degrees to 30degrees flexion. The iliotibial band had a significant stabilizing effect from 0degrees to 30degrees flexion.