In Vivo Knee Loading Measured by an Instrumented Total Knee Replacement during Activities of Daily Living

The knee sustains large contact forces over a broad range of flexion angles. The flexion angle where the largest forces occur during specific activities is an important consideration for understanding both normal and pathological conditions, since the position of the tibial-femoral contact is related to the activity, the phase of the activity, and knee flexion angle (Dyrby and Andriacchi, JOR 2004, Andriacchi and Dyrby, JBiomech 2005). Variations in the thickness of healthy knee cartilage suggests that in regions of habitual loading, stance phase knee flexion during walking, shows thicker regions of cartilage and thinner regions where it is less likely to be loaded (Andriacchi TP et al. 2004). The relationship between knee loads at high flexion angles is also an important consideration. For example, the incidence of osteoarthritis is substantially higher (15% to 30%) in workers who performed deep knee bends as part of their job, than in the general population (Felson et al. 2000). Thus, when analyzing the influence of knee loading on disease processes or in evaluating design criteria for total joint replacement it is important to consider specific activities. The overall goal of this study was to examine the relationship between activity, load, and flexion angle where maximum load occurs for walking, stair ascending and descending, chair rising and sitting, squatting and golf swing. METHODS