Double Condyles Contact Force Estimation of Knee Joint Based on Hill-Type Model

Abnormal joint loads in vivo accelerate the development of knee osteoarthritis and lead to functional degradation of the biological/artificial knee. Quantification of double condyles contact force of knee joint is crucial for clinical gait assessment. In this paper, muscle moment was calculated based on Hill model and external knee adduction moment (KAM) was estimated by using back propagation neural network (BPNN). Considering both contributions, the knee contact force (KCF) was calculated. The whole body musculoskeletal model was established based on OpenSim, with three degrees of freedom (DOF) and double contact points at knee joint. The reliability of the model was verified by 21 gait trials at free pace (1.19±0.09m/s) of four subjects who underwent total knee arthroplasty (TKA). The results showed that the value of proposed modeling estimation was highly correlated with those of implant measurement in the surgical knee. The Pearson Correlation Coefficients (ρ) of the medial/lateral knee contact force (MKCF/LKCF) were 0.93±0.06 and 0.81±0.16. Peak error and time error were less than 0.40 body weight (BW) and 50ms. The estimation of proposed modeling was also highly correlated with simulation of OpenSim in the healthy knee. It was concluded that reliable KCF could be obtained using the proposed model.