Anatomy of the Hip
The hip joint is a “ball and socket” joint. The “ball” is known anatomically as the femoral head; the “socket” is the part of the pelvis known as the acetabulum. Both the femoral head and the acetabulum are coated with articular cartilage. Like all joints, the hip has synovial or joint fluid, acting as a lubricant, which allows for smooth, painless movement within the hip joint.
The labrum of the hip, similar to that of the shoulder, is a ring of rubbery fibrocartilage around the rim of the acetabulum, which deepens the hip socket and acts as the suction seal of the hip joint. The intact labrum seals the lubricating fluid within the hip and contributes to stability of the joint. One of the most common causes of hip pain involves damage to the labrum, described most often as a labral tear. When the labrum is torn, the “suction seal” is broken, and the joint may lose its stability and lubrication. This can progress to loss of cartilage or arthritis.
Degenerative changes to the hip can also result in arthritis. Arthritis is the damage to the articular cartilage of the joint that lines on the head of the femur and the acetabulum or socket. The joint capsule is an envelope of ligaments that encloses the hip and is also essential for stability. The hip also contains a ligament known as the ligamentum teres, which connects the femoral head to the acetabulum. Both the capsule and the ligamentum teres can be injured in an unstable hip.
The capsule is an envelope of ligaments which encloses the hip providing increased stability.
The ligamentum teres is another ligament, inside the hip joint, which connects the femoral head to the acetabulum. Both the capsule and the ligamentum teres can be injured in an unstable hip.
The Iliopsoas muscle is comprised of three distinct muscles: the iliacus, psoas major and psoas minor. These muscles are fused together laterally by the iliopsoas tendon and cross the hip joint to connect with the lesser trochanter of the femur. The iliopsoas serves to flex and externally rotate the leg and is needed in standing, walking and running.
The gluteus medius is one of three gluteal muscles. It is located on the outer surface of the pelvis. Due to its location relative to the hip joint, the gluteus medius is important for leg abduction or lateral movements away from the midline of the body.