Hip joint forces during load carrying.

In some diseases affecting only 1 hip joint, it is necessary to keep the contact force between femoral head and acetabulum (hip joint force) permanently low at the affected side. Six subjects were examined while they were walking and carrying a load in 1 or 2 hands. It was determined how the forces in both hip joints are influenced by the magnitude of the load and the manner in which it is carried. A mathematical model was used to calculate the maximum forces in the frontal plane. One subject had instrumented endoprostheses implanted in both hips. For him the measured values were slightly higher than the calculated ones, but the overall results were similar. Carrying a load on 1 side keeps the force constant at the ipsilateral hip joint or even slightly lowers it. At the same time, there is a large increase on the opposite side. Carrying 25% of body weight with 1 hand causes about 2/3 higher forces in the contralateral joint than on the loaded side. If this load is evenly distributed between the 2 sides, both hip joint forces increase by 25%. In unilateral load carrying, additional relief of the ipsilateral joint can be achieved if the upper body is held upright and the loadcarrying arm is abducted, such as when using a large shopping basket.