[Analysis of the shear force exerted on the tibia during standing on bilateral legs with knee flexion]

Biomechanical analysis of the two-dimensional models composed of roentgenographic pictures and electromyographic analysis about the shear force (Fs) exerted on tibia during standing on bilateral legs was conducted in 21 young adult males. The simultaneous contraction of the quadriceps and hamstrings was observed in all electromyograms (EMGs). Amplitude observed on EMGs of the hamstrings increased as the trunk flexion angle increased. The calculated average values of Fs were negative at every knee flexion angle; Negative value means posteriorly directed force. As the trunk flexion angle increased, posterior drawer force increased at knee flexion angles of 30 degrees and 60 degrees. The simultaneous contraction of the quadriceps and the hamstrings was considered to represent the main factor that influenced these results. The standing on bilateral legs with knee and trunk flexion was considered to be applicable in the early stages after anterior cruciate ligament reconstruction.