The hip joint is one of the central movement organs of humans. On the one hand, it serves the proper movement of the leg, and on the other hand, it ensures an elegant gait. The use of the hip joint plays an enormous role in almost all daily activities. It carries a large part of the human load and, in conjunction with all other joints, provides a great freedom of movement.
What is the hip joint?
Thus, the hip joint represents a ball and socket joint in the classical sense. Joints of this type are characterized by the ability to perform circular movements in almost all directions. However, these are limited by ligamentous and muscular apparatuses surrounding the joint. The limitation is based on the elasticity of the muscles.
Anatomy and structure
A hip joint is initially formed by the acetabulum, which sits in the pelvis, and the femoral head, which slides within it and belongs to the femur. The bone surfaces that meet in this process are lined with a layer of cartilage. The socket is located exactly where the ilium, pubis and ischium meet. These two components are held together by a ligamentous connection that runs from the head of the femur to the center of the acetabulum. Furthermore, the joint is surrounded by a strong capsule and other strong overlying ligaments. The muscles are divided into flexors and extensors depending on their function. The most important flexors include the hip-lumbar muscle, the sartorius muscle and the four-headed thigh muscle. The extensors include the large gluteal muscle and the ischial tibial muscles. Furthermore, the medium and small gluteal muscles participate in the movements.
Function and tasks
The muscles surrounding the joint, allow rotational movements. As a result, the leg can be swung through forward and backward in an extended form, as well as raised and lowered. More precisely, the leg can be moved on three axes by the hip joint. During raising and lowering, the leg has a range of motion of 130-140°. On the other axis, it can be abducted 30-45° and even abducted 20-30° beyond the leg next to it. When flexed and raised, it can be rotated in radius between 30-50°, inward and outward respectively. When walking, running or jumping, one side balances the other. This is also the case when one of the two sides of the hip is restricted by an acute or chronic medical condition. Normal gait results from one side’s leg taking over the function of the stance leg, and the other side’s leg passing by it.
Diseases and disorders
Often complaints in the form of pain, can limit the movement of the hip joint. One of the most common diseases of the hip is osteoarthritis – the so-called wear and tear of the joint. In this case, the cartilage surfaces are damaged in the appropriate places due to incorrect, i.e. too high, loading or due to signs of aging. If this happens over a longer period of time, the cartilage can be completely degraded in various areas. There, the bones then rub directly against each other and can cause severe pain in the entire area of the hip joint. If pain of this kind occurs, relief of the damaged joint is often sought. This however, can lead to increased stress on the opposite hip joint. Furthermore, the hip joint arthrosis can also be permanently damaged by an already existing malposition in the hip joint itself. In the case of severe arthrosis, joint replacement by means of a prosthesis, which replaces the worn parts of the joint, can be considered. However, sufficient diagnostics in the form of X-rays or perhaps even a joint endoscopy should be performed beforehand. Hip dysplasia, on the other hand, is essentially a developmental disorder. In this case, the acetabulum is steeper and flatter at the pelvis. This creates the risk of the femoral head sliding beyond the edge of the socket, thus dislocating the hip joint. In summary, the hip joint offers very complex applications due to its relatively simple structure. There is no doubt that it is very stable and robust. Nevertheless, it is important that the hip joint is not exposed to a permanent incorrect load. This is because the consequences of long-term overuse are not immediately visible, but proceed insidiously and are therefore often noticed too late.
