Influence of individual quadriceps and hamstrings muscle architecture and quality on knee adduction and flexion moment in gait

The purpose of this study was to investigate the relationship between muscular parameters of quadriceps/hamstrings and knee joint kinetics in gait. Muscle architecture (thickness, pennation angle, and fascicle length), and quality (echo intensity) of individual quadriceps and hamstrings of 30 healthy participants (16 males and 14 females) was measured using ultrasound. Peak knee flexion moment (KFM), KFM impulse, peak knee adduction moment (KAM), and KAM impulse during walking were obtained at preferred speed. Pearson’s correlation coefficient and multiple regression analyses were performed at significance level of 0.05, and Cohen’s f(2) values were calculated to examine the effect sizes of multiple regression. The hamstring-to-quadriceps muscle thickness ratio (r = 0.373) and semitendinosus echo intensity (r = − 0.371) were predictors of first peak KFM (R(2) = 0.294, P = 0.009, f(2) = 0.42), whereas only vastus medialis (VM) echo intensity was a significant predictor of second peak KFM (r = 0.517, R(2) = 0.267, P = 0.003, f(2) = 0.36). Only the VM thickness was the predictor of first (r = 0.504, R(2) = 0.254, P = 0.005, f(2) = 0.34) and second peak KAM (r = 0.581, R(2) = 0.337, P = 0.001, f(2) = 0.51), and KAM impulse (r = 0.693, R(2) = 0.480, P < 0.001, f(2) = 0.92). In conclusion, the greater hamstring-to-quadriceps muscle thickness ratio and the muscle architecture and quality of medial quadriceps/hamstring play an important role in KFM and KAM, and may have implications in knee osteoarthritis.