Biomechanics in orthopaedics is a wide field which deals with the application of laws of mechanics on the human locomotor system. Understanding its fundamental rules calls for knowledge of physics, basic mathematics and diverse fields of medicine, particularly the anatomy of the locomotor system and orthopaedics. From a biomechanical perspective joints can be viewed as centres of the rotation axis, and limbs as levers. Jointed bodies achieve equilibrium if moments of force on both of the sides are equal, whereby mostly on one side there is the effect of weight of the examined body part, and on the other there is muscular force opposed to that weight in order to keep the balance. Contemporary biomechanical approaches are now used on the hip joint. Biomechanically, the hip joint is best examined when standing up straight on both legs, whereby the force is equally divided between both joints and the median runs through the centre of the pelvis, along the spine. In the case of the hip joint, there are two levers on which forces are exerted – the lateral, which is the place where the muscular force is exerted, and the medial lever, which is where the body’s weight acts. Joint stress is significantly higher when standing on one leg or when walking. Maintaining stability of the hip joint is important for keeping the body stable in space and for moving. In addition to the work of the hip joint, this is also accomplished by the knee joint, the largest joint in the human body. Both the hip and the knee joints are under constant pressure. Orthopaedic biomechanics focuses on the effect of forces on particular changes taking place in the joints and the impact these changes have on the development of biomechanical dysfunctions. The principal clinical sign of dysfunctional hip joint or knee joint is limping. Apart from some causes not related to biomechanics, one of the causes of deviations from the normal gait pattern is abnormal exertion of forces on the joint, often leading to a compensatory pathological gait so as to keep the balance. The effects of wearing various types of footwear, such as high heels by women, on changes in the knee joints are problems focused on by biomechanics. In addition to this, it deals with the issue of using a walking cane held contralateral to the affected hip so as to reduce the torque by reducing the body’s weight, and analyzes the acting of forces on the knee joint when performing squats.