Analysis of the Method for Estimating the Hip Joint Centre for determination of the Hip and Knee Joint Angles

The study of the human gait through the joints angles is an important branch of the biomechanics. The joints angles define the behavior of a segment in relation to another and, consequently, the overload on the tissues. The hip joint centre (HJC), regression equations system based on pelvic anatomy, is a parameter frequently used as reference point to determinate the hip and knee angles, therefore, is considered in the literature as an important factor in the kinemactics analysis of the human gait. Two analytical methods are recognized in the HJC estimation, the predictive method uses the difference between the anatomical points of the human body in the data collect, and the functional method uses a sphere adjustment approach. In the present research, it was used kinemactics data from seven volunteers, collected by Qualisys® system on a treadmill, and through algorithms developed in MATLAB®, the HJC were estimated by two predictive method systems (Bell and Davis) and one system of the functional method (with sphere adjustment approach based on the StarArc movement) and the joints angles which describes the flexion/extension movement of the hip and the knee were determined. Finally, a study was carried out on the influence of the methods for HJC estimation in the determination of hip and knee joints angles. The errors presented in the HJC estimated by the three methods were documented, but did not present significant influence in the values found by the angles of the joints.