This month’s anatomy series looks at the hip joint. Like the shoulder that was discussed last month, the hip is a ball and socket joint. But unlike the shoulder, the hip socket is quite deep which drastically improves the joints stability but as a result loses some of the freedom of movement that the shoulder enjoys.
The hip joint is made up as the head of the large thigh bone called the femur, sits in a socket located on the side of the pelvis. The socket, or acetabulum, almost entirely encompasses the hemispherical head of the femur and contributes substantially to joint stability. The entire periphery of the acetabulum is rimmed by a ring of wedge-shaped fibrocartilage called the acetabular labrum. The labrum deepens the socket and increases the joints concavity. Adding to this stability is a group of ligaments that support the internal and external surfaces of the joint.
There is a myriad of muscle attachments in and around the hip joint. The different muscle groups act upon the hip and pelvis to work as stabilisers or powerful movers of the lower limb. The muscle groups can be divided into the adductors (groin), hip flexors, glutes, deep hip rotators, and the hamstrings. Attaching to the glutes and another muscle, the tensor fascia lata, is the iliotibial band. The ITB is a strong fibrous rope-like structure that runs down the outside of the leg. The action of the ITB and its associated muscles is to flex, abduct, and medially rotate the hip. The ITB additionally contributes to lateral knee stabilisation.
Common hip injuries seen in the clinic include muscle strains of the adductors and hamstrings, labral tears, hip joint osteoarthritis, stress fractures, tendonopathies, bursitis, and biomechanical problems related to muscle imbalances. With the multitude of different structures that help comprise the hip joint, it is important that correct and early diagnosis of hip pain be made. This will result in the reduction of pain and earlier return to functional activities
