Identification of the hip and knee angles that hamstring muscles exert knee extension function

Abstract

Previous studies suggested a probability that hamstring muscles (HAM) can exert knee extension function in some specific hip and knee angles, even though HAM were classified knee flexors. However, it has been still unclear in what the hip and knee angles HAM exert knee extension function. The purpose of this study is to reveal the relationship between the hip and knee angles and hamstring muscles function on the knee joint by using numerical simulation. OpenSim, a free musculoskeletal model software, was used to construct the numerical simulation. Semimembranosus (SM), semitendinosus (ST), biceps femoris long head (BFLH), and biceps femoris short head (BFSH) were selected as the analysis targets. Induced acceleration analysis (IAA) was used to identify the muscle function on the knee joint. IAA could explain the cause-and-effect relationship between exerted muscle force and joint angular acceleration induced by the exerted muscle force. The hip and knee angles conditions were determined by combining the right hip flexion angle that ranged from -30°to 90°and the right knee flexion angle, which ranged from -10°to 90°. As a result, the present study revealed following three things; 1) SM, ST, BFLH, and BFSH function on the knee joint were dynamically changed depending on the hip and knee flexion angles, 2) SM, ST, BFLH exerted knee extension function in the specific hip and knee flexion angles, 3) BFSH did not exert knee extension function. These findings might be a fundamental data to explain the relationship between the hip and knee flexion angle and HAM function on the knee joint.