The role of muscular co-contraction of the hip during movement.

The joint biomechanics of the hip was studied analyzing the kinematic, kinetic, electromyographic and in vivo pressure parameters during walking, going up stairs, and getting up from a chair. The most significant clinical and biomechanical data emerged when the temporal correlation between intra-articular pressure variations and electric activity of the bi-articular muscles was studied. The presence of co-contraction of the bi-articular muscles during the support and oscillation phases was evident. The maximum joint pressure values were measured while getting up from a chair when the hip was flexed more than 100 degrees. The posterior region of the acetabulum was that most submitted to loading. This data is useful in gaining an understanding of joint physiology, in correctly setting up physio-kinesitherapeutic protocols, and in setting up pre-clinical prosthetic mechanical tests.