The hip is comprised of the hip bones as well as the muscles and tendons which are attached and form part of the overall hip structure.
The Hip Bones
The main bony structure of the hip, which has a socket joint at each side where the thighbones connect. It comprises the 'ileum' at the rear, the 'pubis' at the front and below the pubis the 'ischium'.
This is the thighbone which attaches to the pelvis with a ball and socket joint, with the ball part at the top of the femur (referred to as the 'femoral head') and the socket (the 'acetabulum') in the pelvis.
This structure is the largest ball and socket type joint in the human body and needs to allow for a wide range of motion so that running, walking and climbing are possible as well as other more complex movements, such as pointing the toes and feet in and out (which allows us to cross our legs and to squat for example).
The Muscles and Tendons
The large muscles in the thighs and the buttocks form part of the hip structure. The muscles in the buttocks - the gluteal muscles - are attached to a bony protuberance at the top of the femur called the 'greater trochanter'. Over the top of the gluteal muscles runs the 'ileotibial band' (or 'ITB') - a long tendon that runs from the hip to the knee, which helps with stability when walking or running.
Other muscles included in the hip structure are...
- Adductor muscles, located on the inside of the thighs.
- Iliopsoas muscle, a hip flexor muscle attached to the upper femur.
- Rectus femoris muscle - a quadricep muscle at the front of the thigh.
Other Hip Components
These are small fluid filled sacs which act as a form of cushion where the muscles, bones and tendons in the hip area rub against each other. There are around twenty of these in the hip area. When these become inflamed or damaged this can cause pain, known as 'bursitis', with a particular form of bursitis called 'trochanteric bursitis' affecting the outer part of the hip.
The 'articular cartilage' in the hip joint sits between the femoral head and the acetabulum and allows the ball and socket joint to work smoothly. It is around 6mm thick and is 'lubricated' by fluid produced in the lining of the joint - the 'synovial membrane'. The lubrication and cushioning provided by the cartilage is particularly important in the hip as the stresses on the hip can be five times the body weight when walking. Pain and swelling can result where cartilage is damaged in some way, either by injury (trauma) or hip arthritis.