Weight bearing area during gait in normal and dysplastic hips.

The size and the shape of the weight bearing area in adult human hips depend on the forces acting in the hip and therefore change during the body motion. In this work the size and the shape of the weight bearing area in several phases of gait are estimated. The forces acting in the hip were determined through laboratory measurements and analyzed by mathematical models. The dysplastic hips are distinguished from the normal ones by a smaller center-edge angle of Wiberg while the time course of the forces acting in the hip is assumed to be the same in both cases. It is shown how radial articular stress is distributed over the weight bearing area in both cases. In normal human hips the weight bearing area occupies a rather large portion of the acetabulum-femoral head contact area while in dysplastic hips stress distribution is unfavourably concentrated in a smaller weight bearing area.