The hip is located on the human body between the trunk and thigh. It enables the upright stance as well as the mobility of the leg, which makes walking possible and at the same time the body is stabilized by the hip. Diseases of the hip thus have essential effects on mobility and walking ability.
What is the hip made of?
The hip consists of the two hip joints and encompasses the pelvic region. Due to its shape, the hip joint is a so-called ball and socket joint, through which the thigh can move in all directions. It is the second largest joint in the human body after the knee joint. The hip joint is also one of the joints that are subjected to the most stress.
Anatomy and structure
The hip joint is formed from the acetabulum (hip socket), the coxae (hip bone), and the caput ossis femoris (femoral head). The ilium arises from the fusion of the ilium, pubis, and ischium. The femoral head is the upper end of the femur and is embedded in the acetabulum, a part of the pelvis. The femoral head is more than half surrounded by the acetabulum in the healthy hip. The acetabulum is widened by a fibrocartilaginous ring called the articular lip or labrum acetabulare. The femoral head and acetabulum are covered with a layer of cartilage and encased by the hip joint capsule, called the capsula articularis coxae. The inside of the joint capsule produces the synovial fluid, or synovial fluid. The synovial fluid provides nutrients to the cartilage of the femoral head and acetabulum and lubricates the joint, allowing smooth movement of the hip joint. The joint capsule is stabilized by several strong ligaments that prevent the hip joint from dislocating. In addition, the hip joint is surrounded by strong muscles.
Function and tasks
The hip joint, together with the surrounding muscles and ligaments, secures numerous movements of the human body. It can be moved three-dimensionally and thereby enables bending and stretching as well as abduction and approach movements and inward and outward rotations. The hip joint allows the leg to move and the function of the hip is crucial for the gait pattern. However, the hip joint not only ensures numerous movements and a wide range of motion, but also acts as a kind of shock absorber during walking and jumping, as well as during bumps and blows. In addition, the hip stabilizes the body when standing, thus enabling an upright stance. Because of its functions, the hip joint supports a large portion of human weight, making it susceptible to wear and tear.
Diseases and pain
Diseases of the hip usually lead to hip pain and limitations in mobility. However, a morning ache after getting out of bed, stiffness after rest, a swollen joint, and grinding or rubbing sounds can also be signs of hip disease. The most common hip disease found in adults is coxarthrosis. Coxarthrosis is a wear and tear of the hip joint in which the cartilage layer of the femoral head and acetabulum is damaged. The symptoms often start with pain when walking and increase in the advanced stage of coxarthrosis to pain that also occurs at rest. Increasing restriction of the hip may occasionally result in knee pain as well. Patients show a typical gait pattern that is caused by a protective posture of the hip. If the reason for the development of coxarthrosis is not known, doctors speak of ideopathic or primary coxarthrosis. If the reason is known, it is a secondary coxarthrosis. In this case, the causes of wear and tear may already be due to childhood conditions, such as hip dysplasia. Other causes of secondary coxarthrosis are often femoral head necrosis, a hip fracture due to an accident, or inflammatory diseases such as rheumatism. Rarely, metabolic diseases such as gout or infections of the joint can also lead to secondary coxarthrosis. Osteonecrosis of the femoral head results in the death of bone tissue, destroying the bone at the femoral head. Inflammation of the hip joint is rare but very painful. Other conditions of the hip may include bursitis, a condition called bursitis, a labral lesion, or hip impingement. Bursitis causes pain in the hip or groin area.Labrum lesion is a tear of the joint lip, which limits the mobility of the hip. In hip impingement, ossification causes a narrowing between the femoral head and acetabulum, which can cause the bones to collide during severe flexion. This, in turn, can lead to injury to the joint lip or cartilage if they become pinched. In hip impingement, there is severe, stabbing pain in the groin area. The most common congenital hip disorder in children is hip dysplasia. In hip dysplasia, the acetabulum is not fully formed and therefore does not enclose the femoral head as in a healthy hip. Other hip disorders in children and adolescents that can cause hip pain include Perthes disease, epiphysiolysis capitis femoris, and coxitis fugax. In Perthes disease, bone tissue in the femoral head dies. Affected children limp, have pain in the knees and limited mobility of the hip. Epiphysiolysis capitis femoris is the name given to a detachment of the femoral head. There is pain in the hip or knee. Coxitis fugax is the so-called hip rhinitis, in which the hip joint is inflamed it, but no germs are the triggers for the inflammation. Affected children limp and have knee pain.