Effects of Pedaling Direction on Knee Ligament and Articular Surface Loading During Cycling

Cycling has many functionality in our daily life. It is also widely applied to the rehabilitation of the lower extremities, and it can be classified according to the pedaling direction as forward pedaling and backward pedaling. The knee ligaments and articular cartilages has a great influence on the knee joint stability. Because of the highest utilization rate, knee injuries with soft tissues is common, especially cruciate ligament injuries. Finite element method is used to study in vivo joint soft tissue mechanics in the non-invasive measurement. The geometry model is from the three-dimensional reconstruction of the computer tomography and magnetic resonance imaging scan. Material parameters of soft tissues referred the KT-2000 arthrometer and literatures. Boundary condition is acquired from the dynamic fluoroscopy system. The objective of this study was to analysis the loading of the in vivo knee ligaments and articular cartilages in forward and backward pedaling with validated finite element analysis procedure. It will provide a mechanical analysis basis of knee complicated soft tissues in the future. According to the finite element analysis results in cycling, the main representative of the loads in soft tissues were PCL and the medial cartilage. The ligament loads decline in the knee extension and increase in the knee flexion. The articular surface loads show three peak loads (crank angle of 45°, 135° and 280°) and the maximum contact load is 2 ~ 4 times body weight. The effect on pedaling direction is less on the ligament loading. In backward pedaling, it needs more articular surface loading in knee extension and less in knee flexion. In early rehabilitation treatment, the patients with ACL injury and the patients with cartilage damage are suitable for backward pedaling. Cycling is not appropriate for PCL injury patients.