Hip joint contact forces in normal subjects and subjects with total hip prostheses: walking and stair and ramp negotiation

Objective. To calculate the hip joint contact force in normal subjects and subjects with total hip replacements. Design. An observational study of age matched normal subjects and subjects with hip joint replacements. Background. Hip joint contact forces have been calculated using musculo-skeletal models and measured in vivo using instrumented hip prostheses. There are few examples of studies performed on subjects in the 40–60 year age range. This study characterises the forces in both normal subjects and subjects with hip joint replacements for these ‘youngʹ subjects. Methods. Motion analysis and force plate data were used as input to a three-dimensional model of the leg. Five male and six female normal subjects and five male subjects with hip prostheses were studied. Each subject was observed walking and negotiating stairs and a ramp. Results. Hip joint contact forces in both thigh and pelvic-based co-ordinate systems are presented. Subjects cadence, speed and stride length are given. Conclusions. In general subjects with hip replacements exhibited lower hip joint contact forces than age matched normal subjects. It is suggested that this was the results of the lower speeds, stride lengths and cadences adopted by the subjects with hip replacements.