Knee Joint Biomechanics during Cycling in Patients with Total Knee Arthroplasty

INTRODUCTION Cycling is a recommended activity after total knee arthroplasty (TKA) and it has been shown that up to 50 % of the TKA patients are riding a bike and 25 % think that cycling has an important place in their life. In a recent in vitro study [1], which investigated the contact pressures in TKA components for common recreational activities (cycling, power walking, downhill walking, jogging), it has been concluded that cycling produces relatively low contact forces and therefore is a safe activity for TKA patients. The explored quasi-static approach, however, bears certain limitations which need to be considered. Cycling is an activity with relatively high flexion demand. Sagittal plane angles of 110 degrees and more are typical. The combination of high flexion together with antero-posterior motion and/or internal/external rotation may cause unfavorable conditions at the artificial articulation leading to constraint forces and subsequent wear (even though external forces are low). The purpose of this study was to analyze the three-dimensional motion pattern of the knee joint during cycling for a group of TKA patients compared with a normal control group. In addition, kinetic boundary conditions were obtained to better describe the biomechanical situation.