Factors affecting flexion after total knee arthroplasty.

UNLABELLED: Results of total knee arthroplasty have demonstrated excellent pain relief and increased patient function, particularly in activities such as walking. This procedure has not always met the needs of certain ethnic and religious groups as well as younger patients who require greater magnitudes of knee flexion. This has resulted in the introduction of new implant designs engineered to improve postoperative flexion. We reviewed factors known to influence postoperative flexion after total knee arthroplasty. An in vivo, weightbearing fluoroscopic kinematic analysis of multiple high-flexion total knee arthroplasty designs was performed, and demonstrated high levels of weightbearing flexion (125 degrees) can be obtained in some, but not all, evaluated designs. Multiple evaluations of the same high-flexion total knee arthroplasty design performed by different surgeons and involving different patient populations revealed one study group with high weightbearing flexion and other groups that did not achieve high flexion. This suggests numerous factors other than implant design influence eventual flexion, including the patient, surgical technique, knee kinematics, perioperative complications, and postoperative physiotherapy. LEVEL OF EVIDENCE: Level V, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.