Noninvasive Assessment of Sagittal Knee Kinematics After Total Knee Arthroplasty

Normative and arthroplasty knee joint kinematics have been studied extensively using a wide range of instrumentation and methodologies. Many of the methods used to assess knee mechanics after total knee arthroplasty (TKA) have failed to create realistic testing conditions in terms of joint load and range of motion. In contrast, motion capture studies facilitate knee assessments during functional, weight-bearing activities. Using motion capture techniques, this study aimed to examine differences in sagittal tendon kinematics between TKA and normative individuals. The relative positions of the patellar tendon and quadriceps tendon, as a function of knee flexion-extension, were estimated during step down and bilateral deep knee bend tasks. To assess the validity of this technique, motion capture data were compared to radiographic data for each TKA patient. Sagittal knee tendon angles were measured directly from the radiographs and compared to corresponding points in the dynamic data. Results of the patellar and quadriceps tendon angles showed good agreement between the two methods, with absolute errors ranging from 2.9o to 5.6o, suggesting that noninvasive motion capture is a suitable method for evaluating knee mechanics.