New insights into femoroacetabular syndrome using in-silico assessment of muscle and contact forces

The study consisted of examining coxo-femoral joint kinematics, in-silico muscle force contributions and hip contact forces during level walking and squatting in femoroacetabular impingement syndrome (FAIS). Eleven symptomatic FAIS patients, and 11 healthy participants gave written consent to participate in the study. Motion capture and electromyography were collected to obtain joint kinematics and kinetics as well as muscle activity of the lower-limb muscles during dynamic tasks. Muscle and hip contact forces were calculated in a musculoskeletal simulation program for walking and modified MSK model for the squat task. The findings suggested that the kinematics and hip loading alterations in FAIS might be due to a protective mechanism to prevent higher loads at the anterior-superior femoral head location. The long-term effect of the hip loading protection mechanism has the effect of changing the pattern of muscle contraction that does not seem to recover after treatment.