Surgical Techniques to Achieve Full Extension

Residual extension limitation after TKA is considered as a contributing factor to poor clinical outcomes [1]. Biomechanical studies using cadaveric knees have shown that the quadriceps muscle required 22% more strength to stabilize the knee joint against loading stresses in 15° flexion than in full extension [2]. A gait analysis study of normal knees with orthotic extension restriction showed that the leg length difference and the left-right difference in stride length applied unnatural stress to both knees, increasing the extension moment and adduction moment by up to 15% in the knee with 15° extension restriction [3]. Extension restriction also affected the trunk alignments; the coronal plane showed that the trunk tilted toward the extension-limited side during standing and walking, while the sagittal plane showed increased pelvic posterior tilt during standing and anterior tilt during walking [4]. In a study of postoperative TKA patients with residual limitation of extension, it was shown that the load during gait was increased on the nonoperated knee [5]. In a clinical study of more than 5000 patients who were evaluated over a minimum of 3 years, patients with residual limitation of 10° or more showed significantly lower Knee Society Scores for pain and function items than those of patients who achieved full extension [6]. Another study reported significantly lower Oxford Score and satisfaction in the patients with extension limitation [7]. The postoperative extension limitation tends to improve between 3 months and 2 years [8, 9], however, it was reported that if extension limitation remained greater than 15° at 3 months postoperatively, the risk of residual limitation greater than 5°was high at 2 years postoperatively [10]. Although an immediate postoperative extension limitation of approximately 10° may be acceptable, the goal should be to achieve a fully extendable knee after the surgery.