What Is It?

In the normal hip joint, the rounded top of the thigh bone (femur) fits into a cup-shaped socket in the pelvis called the acetabulum. This type of joint is called a ball-and-socket joint. In a hip dislocation, the top of the femur moves out of its normal position in the socket.

Traumatic hip dislocation is an orthopedic emergency that can occur in accident victims of any age.

Traumatic hip dislocation usually occurs in adults who fall from a high place or who are involved in a motorcycle accident or car collision. When this injury occurs in a head-on car crash, it is often nicknamed a “dashboard dislocation,” because it happens when the knee strikes the dashboard. The force of the knee impact is transmitted back through the thigh to the hip, and this moves the head of the femur out of the joint toward the back of the body.

Traumatic hip dislocation requires immediate treatment, ideally within six hours. That is because a traumatic hip dislocation interrupts the normal blood circulation to the top of the femur, depriving the bone of its vital oxygen supply. Unless the dislocated hip is replaced in its socket promptly and normal circulation is restored within the hip joint, there can be permanent damage to the top portion of the femur. This permanent damage is called avascular necrosis.

Because traumatic hip dislocations often occur during serious high-impact accidents, up to 50 percent of patients also have a fractured bone in some part of the body, particularly in the upper portion of the femur.

In an accident victim, a traumatic hip dislocation can cause the following symptoms:

• There is severe hip pain, especially when the leg is moved.
• The injured leg is shorter than the uninjured leg.
• The injured leg lies in an abnormal position. In most cases, the leg is bent at the hip, turned inward and pulled toward the middle of the body.

Doctors usually diagnose a traumatic hip dislocation by examining the hip joint. X-rays will be done to confirm the diagnosis, determine the direction of the dislocation and to check for fractures in the hip area. In some cases, a computed tomography (CT) scan or magnetic resonance imaging (MRI) may be helpful to provide additional details about the nature of the injury and to help determine the best treatment.

The hip will have some immediate improvement in function after initial treatment and pain should subside. It is common, however, for a person to require crutches for a short time after treatment and to have a limp that continues for weeks. Complete healing of the hip and surrounding tissue can take two or three months. In order to minimize the risk of repeated dislocations, a formal strengthening program may be prescribed. This can improve the support of muscles and ligaments surrounding the hip.

A person with significant pain after a hip dislocation may have developed the complication avascular necrosis from injury to the hip’s blood supply. Avascular necrosis may require surgery, and can prolong the recovery period substantially.

Wear a seat belt while driving or riding in a car, and take advantage of recommended safety equipment to prevent falls if your job requires working in high places.

If you have a traumatic hip dislocation, and there is no X-ray evidence of a fractured femur, the doctor probably will treat the dislocation in the emergency room without surgery. To accomplish this, the doctor will give you medications to ease your pain and relax your hip muscles. Once your hip muscles are relaxed, the doctor will maneuver the head of your femur back into its socket. X-rays will confirm that its position is correct.

If you have a fractured femur in addition to your hip dislocation, your doctor will correct both injuries surgically.

Call your doctor immediately if you cannot move your hip joint following a fall or other traumatic injury, or if your affected hip is painful, swollen, tender or deformed.

Although the prognosis depends on many factors, the timing of treatment is particularly important. For example, one study showed that 88 percent of patients had good or excellent results if a dislocated hip was restored to its normal position in its socket within six hours after injury. After six hours, the risk of permanent damage increased significantly, and it was highest when treatment was delayed for 24 hours or more.

About 20 percent of people who do not develop avascular necrosis eventually suffer from early arthritis in the affected hip.

Diseases and Conditions Center

All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.