Engineering plays a significant role in the advancement of medicine. One example of this is endoprostheses, which are prostheses implanted inside the body. Hip joint endoprostheses are commonly implanted nowadays, greatly improving physical fitness and the associated quality of life. However, a potential risk in using such endoprostheses is the possibility of dislocation. In this presented work, systems of forces acting on the limb were subjected to analysis, identifying unstable states that increase the risk of dislocation. Most of the analyses are qualitative, presenting rather than solving the problem. Nevertheless, a quantitative approach was presented for the case of dynamic forces generated during kicking a soccer ball. For this purpose, computer simulation was employed, based on an appropriate mathematical model.