The effect of medial hamstring weakness on knee contact forces during running

Abstract

When used to reconstruct the anterior cruciate ligament (ACL), the medial hamstrings graft has been shown to produce lower rates of osteoarthritis (OA) than the patellar tendon graft. The goal of this study was to determine how reducing medial hamstring strength during surgery affects joint contact forces during loading, and hence the joint’s proclivity towards OA. A previously developed model of the entire body was used to perform a muscle-actuated forward dynamics simulation of running for two cases: normal muscle strength and medial hamstrings (i.e. semitendinosus and gracilis) weakened by 30%. The muscle forces from these simulations were then used to actuate a discrete element model in a forward dynamics simulation. Weakening the medial hamstrings caused an overall decrease in total hamstrings force by <1%, total quadriceps force by 2%, and cartilage contact force by 4%. This decreased force may be protective against long-term OA and hence may help explain the lower rates of OA in patients who receive medial hamstring grafts.