The hip is defined as the region on each side of the pelvis. The pelvis bone is made up of three sections, including the following:

• ilium - the broad, flaring portion of the pelvis.

• pubis - the lower, posterior part of the pelvis.

• ischium - one of the bones that help form the hip.

The hip joint is a ball-and-socket joint that allows motion and provides the stability needed to bear body weight.

The socket area, which is inside the pelvis, is called the acetabulum. The ball part of this joint is the top of the leg bone. It joins with the acetabulum to form the hip joint.

The hip is one of the most stable joints in the body. But, its function, bearing the body's weight, makes it susceptible to arthritis due to excessive pressure. Pain in the hip may involve injury to muscles, tendons, or bursae (small fluid-filled sacs that cushion and lubricate joints).

What are common hip problems?

The following are some of the most common hip problems:

• Arthritis - the most common cause of the breakdown of hip tissue. There are three kinds of arthritis that commonly affect the hip, including the following:

  • Osteoarthritis - also referred to as "wear and tear" arthritis; this type of arthritis involves the cartilage that cushions the bones of the hip wearing away, letting the bones then rub together, causing hip pain and stiffness.

  • Rheumatoid arthritis - a disease in which, for unknown reasons, the synovial membrane becomes irritated and produces too much fluid. It damages the cartilage, leading to pain and stiffness.

  • Traumatic arthritis - often the result of an injury or fracture. There are more than 300,000 hospitalizations for hip fractures in the United States every year.

• Avascular necrosis - involves the loss of bone caused by insufficient blood supply, injury, and bone tumors and may lead to a breakdown of the hip joint.

• Bursitis - in this condition, the bursa, a closed fluid-filled sac that functions as a gliding surface to reduce friction between tissues of the body, becomes inflamed. There are two major bursae of the hip, both of which can be associated with stiffness and pain around the hip joint, including the following:

  • Trochanteric bursa is located on the side of the hip and is separated significantly from the actual hip joint by tissue and bone.

  • Ischial bursa - the bursa located in the upper buttock area.

• Hip pointer - a bruise or tear in the muscle that connects to the top of the ilium (the crest of the pelvis, just below the waist). Causes of a hip pointer may include a blow, a fall, or a quick twist or turn of the body.