A Parametric Study on Joint Impact Forces During Landing

Abstract

The aim of this paper is to look into the effect of joint stiffness and leg configuration on impact time and impact forces applied to the joints during drop landing. This study leads to an understanding of whether and how changing these two parameters (e.g. by an external component) can reduce the joint impact forces and the risk of landing injury. Knowing that the joint stiffness is a result of the forces of all the muscles involved in the motion of the joint, studying the effect of joint stiffness on impact phenomenon provides insights regarding how we activate our muscles during landing in reality, which leads to developing an accurate theoretical musculoskeletal model for landing. In this vein, starting with the hip and the knee joints, we study the impact dynamics of drop landing by considering a simple two-link planar manipulator model which comes in contact with the ground. The elasticity and the damping effects of the muscles are expressed by torsion spring-and-dampers in the joints. The effect of the joint stiffness and leg configuration on the impact force is then studied by changing the joints spring-and-damper coefficients and the joints angle prior to the contact. The obtained results are of practical importance in developing landing theoretical models, teaching landing skills and designing orthoses for reducing the joint forces in athletes or patients with joint problems.