Kinematic analysis of posterior-stabilized total knee arthroplasty during standing up from and sitting down on a chair

BACKGROUND Total knee arthroplasty is effective to regain quality of life. Standing up from and sitting down on a chair and stair stepping motion are important in daily living. We previously reported in vivo kinematics of this implant during a stepping exercise. The purpose of this analysis was to assess in vivo knee motion during standing up from and sitting down on a chair and determine the motion pattern in patients with the unique knee prosthesis. METHODS A total of 15 patients implanted with Bi-Surface PS were assessed during standing up from and sitting down on a chair. The Bi-Surface PS knee is a posterior-cruciate substitute prosthesis with a unique ball-and-socket joint in the mid-posterior portion of the femoral and tibial components. Patients were examined during standing up from and sitting down on a chair using a two-dimensional to three-dimensional registration technique. RESULTS During standing up from and sitting down on a chair from minimum to 30° knee flexion, anterior femoral translation was slight. From 30° knee flexion to maximum flexion, the kinematic pattern was a medial pivot and rollback. CONCLUSIONS This study demonstrated that the knee motion kinematic patterns observed in this study were not similar to normal knee kinematics and derived from the unique design of the Bi-Surface PS.