Soft Tissue Balance/Joint Stability: Anteroposterior Stability

Adequate anteroposterior stability plays a crucial role in total knee arthroplasty (TKA), as it enables rollback or backward sliding of the femoral component associated with flexion, which theoretically improves range of motion (ROM). The cruciate retaining (CR) design aims to prevent femur impingement with the posterior part of the tibia in early flexion by using the posterior cruciate ligament (PCL) tension with knee flexion to induce rollback. Conversely, the cruciate substituting (CS) design aims to prevent early impingement by preventing excessive roll forward or forward sliding through the post-cam mechanism. Recent designs, such as bicruciate-retaining and bicruciate-stabilizing designs, also rely on the movement of the remaining ligaments or their compensatory shapes to prevent impingement between the femur and tibia during early flexion. Therefore, good clinical results, especially large knee flexion angles, are expected owing to moderate anteroposterior stability after TKA, regardless of the design. An adequate flexion angle not only benefits the activities of the daily life of the patient but also contributes to increased satisfaction [1]. Therefore, the surgeon must understand the optimal stability requirements associated with the chosen designs.