The hip joint is a complex, major and large sized joint of the lower limb. It is deeply located in the groin area and connects the lower limb with the axial skeleton.

Hip joint is a ‘ball and socket’ type of articulation. The head of the femur (upper part of the thigh bone) forms the ball part of the joint and it articulates with a socket called the acetabulum (a part of the pelvis bone). Both the femoral head and the acetabulum are covered with hyaline cartilage that reduces friction between the bones and allows smooth gliding movements of the hip joint.

A strong and flexible ring of cartilage, called the labrum, sits on rim of the bony socket of the hip joint. The labrum has many functions including shock absorption, joint lubrication, pressure distribution and providing stability to the hip joint by deepening the socket.

The hip joint has a thick capsule along with strong ligaments, muscles and tendons to provide support, stability and the ability to move the lower limb in different planes. The joint is also lined on the inside by the synovial membrane, which produces the synovial fluid. This fluid helps in lubricating the hip joint and nourishing its articular cartilage. Small sacs of synovial fluid, called bursae, surround the hip joint. Whenever the hip joint moves, these bursae help in providing protection from friction to the bones, muscles and tendons of the hip joint.

The hip joint helps support our body weight, during standing as well as in motion, and allows various movements at this joint without pain. Weight-bearing stresses on the hip during walking can be 5 times a person’s body weight.

Changes in the hip from disease or injury will significantly affect a patient’s gait and place abnormal stress on joints above and below the hip. It takes a strong force to seriously damage a hip joint because the joint is deep seated and is surrounded by strong capsular ligaments and large muscles of the thigh.