A biomechanics-based conceptual design of spring knee-aid

Occupational activities that require high knee-flexion tasks are associated with a higher prevalence of knee osteoarthritis (OA) compared to the general population. Spring knee-aids have been used to protect the knee joints during dynamic high knee-flexion tasks. The objective of this study was to develop a biomechanical model to analyze the knee joint mechanics during deep squatting while wearing various conceptually designed knee aids. The musculoskeletal loadings in the knees were calculated using inverse dynamic modeling. Commercially available software AnyBody (version 7.2) was used for the analysis. In deep squatting, the back of the thighs will contact the calves, influencing the joint contact forces. An analytical approach to consider the effects of the thigh-calf contact interactions was derived and implemented to the AnyBody model. The knee joint loading for deep squatting tasks without knee aids were compared with those wearing knee aids of different spring stiffness levels. The current biomechanical modeling predictions indicate that the use of typical commercial spring knee-aids helps to reduce the contact forces in the tibiofemoral (TF) and patellofemoral (PF) joints by approximately 7-8%, and that the effects of the knee aids in reducing musculoskeletal loading can be enhanced about four times by increasing the spring stiffness of the knee aids by 1-3 times. The current analysis provides a biomechanical basis for improving the design of commercially available knee aids, thereby reducing knee OA in workers frequently performing high knee-flexion tasks.