2003 Hap Paul Award Paper of the International Society for Technology in Arthroplasty. Design and activity dependence of kinematics in fixed and mobile-bearing knee arthroplasties.

Knee arthroplasty implants are designed with features that provide varying articular constraint over the range of flexion such that the pattern of knee motion may also vary. Because the motions of total knee implants have a direct influence on patient function and device longevity, it is important to understand how knee implants based on a variety of design philosophies perform in vivo. Fifty-nine knees in patients with 5 designs of implants were studied with fluoroscopic imaging during gait and stair-climbing activities. Many knees showed significantly different kinematics between the gait and stair activities, as well as differences from knees having other implant designs. The measured motions were consistent with the intrinsic constraint provided by the implant components and the variation in constraint over the flexion range.