Joint Reaction Force and Contributions of Surrounding Muscles to Knee Joint Load during Stair Ascent in Total Knee Replacement Patients and Healthy Individuals

Total knee replacement (TKR) is commonly used to correct end stage knee osteoarthritis (OA) of the knee joint. Unfortunately, difficulty with stair climbing has been seen to exist, prolonging the challenges of TKR patents. Complete understanding of loading at the knee is of great interest in order to aid patient populations, implant manufacturers, rehabilitation, and future research. The outcome of a TKR is intended to reestablish normal motion and loading of the knee. Musculoskeletal modeling provides a means to accurately approximate joint loading and the corresponding muscle contributions during a movement.

The purpose of the present study was to examine if the knee joint loading are recovered to the level of healthy individuals following a TKR, and determine the contribution of the muscles to knee joint loading. Data from five healthy and five TKR patients were selected for musculoskeletal simulation using Opensim. Variables of interest included knee joint reaction forces and the corresponding muscle forces. A paired samples t-test was used to detect difference between groups for each variable of interest with an alpha level set at 0.05 a priori.

TKR patients showed a trend of having higher 2^nd peak compressive JRF than healthy individuals. Some muscle compensatory strategies appear to be present in the push-off phase; however the differences in muscles do not clearly explain the trend present in compressive JRF during the 2^nd 50% of stance. Evidence from knee extension moment and muscle force contributions during the loading response phase indicates reduced muscle strength in the knee extensors of TKR patients. This result combined with greater flexor muscle force resulted in similar compressive JRF during loading response between groups.