Fig. 1. Postoperative radiographs showing insufficiency due to progressive weakening of the posterior cruciate ligament (PCL) tension. (A) One-year postoperative (right knee) and 14-year postoperative (left knee) radiographs after cruciate-retaining total knee arthroplasty (CR TKA); the sagittal angle of the CR TKA was 0.9° of flexion. (B) Three-year postoperative (right knee) and 17-year postoperative (left knee) radiographs after CR TKA. Gradual insufficiency of the PCL tension caused hyperextension of the left knee although she had no clinical instability symptoms and limited range of motion; the sagittal angle was 10.5° of hyperextension.
