The hip is a ball and socket joint, with the socket (acetabulum) in the pelvis meeting the ball (femoral head) located on the upper end of the thigh bone (femur). It is a very stable joint because of the deep socket which limits hip motion. The most common clinical conditions involving the hip include osteo or rheumatoid arthritis, fracture, or dislocation.

Hip Fracture
Fracture of the hip is a common injury in the elderly patient after a fall, due to the weakening of bone which occurs with aging. The fracture can be in the femoral neck or in the trochanteric area. Where the fracture occurs, the degree of displacement, the number of fractures, and the age of the patient are all considered while determining the type of treatment needed, which is almost always surgical. Undisplaced and minimally displaced fractures of the femoral neck are usually treated with pins or screws placed across the fracture. Displaced femoral neck fractures, particularly in those who are advanced in age, are often treated with removal of the femoral head and neck and insertion of a femoral hip prosthesis, similar to a total hip femoral component, into the canal inside the upper femur, which allows early walking with weight bearing. Fractures of the trochanteric area are treated with screws inside the femoral neck which are connected to a plate or rod to stabilize the fractures until they heal.

Complications following hip fractures are primarily those seen in elderly patients following any major surgery: phlebitis, pneumonia, infection, and post-operative confusion

Total Hip Replacement
The total hip prosthesis consists of a metal femoral component which is inserted in the canal inside the upper thigh bone and which moves in the acetabular component, which is a polyethylene socket with metal backing placed in the pelvis. There are no ligaments which hold the components together; because of this, the patients who have total hip surgery must be careful to avoid positions which might dislocate the hip components until the body makes enough scar to stabilize it.

Total hip replacement is a major surgery, and, as such, there are significant risks associated with it. The major risks, in addition to dislocation, include infection, loosening, and breakage of the components, along with medical complications such as blood clots in the leg veins or lungs, pneumonia, or anesthetic complications. Barring complications, total hip surgery has a high rate of success in improving hip pain. Due to the risks, however, it is best used in the elderly patient with hip arthritis.