The Influence of Contemporary Knee Design on High Flexion: A Kinematic Comparison with the Normal Knee

Although >90% of total knee arthroplasties are associated with a good-to-excellent outcome, some patients have difficulty adjusting their gait to accommodate the new articulations inherent in contemporary implant designs. Paradoxical motions inclusive of anterior sliding and lateral pivot are examples of aberrant kinematics in total knee arthroplasty. A computational kinematic simulator measured the motion attained by six contemporary total knee arthroplasty designs. Results were compared with the in vivo kinematic data from healthy knees (i.e., knees with no history of surgery) in deep flexion1. Three designs employing a tibial post and a femoral cam as the motion control mechanism were evaluated, including the Legacy LPS-Flex Fixed Bearing (Zimmer, Warsaw, Indiana), the Journey (Smith and Nephew, Memphis, Tennessee), and the Vanguard PS (Biomet, Warsaw, Indiana). Three designs that did not employ a tibial post and femoral cam mechanism were also evaluated, including the MRK (Finsbury, Leatherhead, United Kingdom), the Duracon (Stryker Orthopaedics, Mahwah, New Jersey), and the Triathlon (Stryker Orthopaedics). All six designs have a fixed plateau and are currently available for clinical use in the United States.