Hip dislocations

[Justin Bieber]

Hip dislocations occur when the ball-shaped head of the thighbone (femur) pops out of the rounded socket of the hip bone (pelvis).

Usually, hips are dislocated when a great force hits a bent knee and pushes the head of the thighbone backward—for example,when a knee hits the dashboard in a car accident.
People with a hip dislocation often have other injuries.
The hip is very painful, and usually people cannot move their leg.
Doctors diagnose these dislocations by examining the hip and taking x-rays.
Doctors can usually put the hip back in place without surgery, typically after giving the person drugs to make the procedure more tolerable.

(See also Overview of Dislocations.)
In most hip dislocations, the head of the thighbone is pushed backward—called a posterior hip dislocation. These dislocations usually occur when the knee and hip are flexed (as when sitting down) and a great force hits the knee. A common cause is hitting the knee against the dashboard of a car in a crash. Hip dislocations can also occur when people fall from a high place (such as a ladder) or play a contact sport (such as football and rugby). In older people, much less force is needed to dislocate a hip.
The force that causes the hip dislocation often also causes other injuries. For example, when a hip dislocation results from a fall or an athletic injury, the pelvis, knee, or legs may be fractured, and the back or head may be injured.
Sometimes children are born with a dislocated or malformed hip (called hip dysplasia). If hip dysplasia is not detected before children start to walk, they may not walk normally, and the hip may not develop normally.
When the hip is dislocated, bones may be broken, and nerves, including the sciatic nerve (see Sciatica), may be injured. The blood supply to the head of the thighbone may be disrupted, causing bone tissue to die (called osteonecrosis).
An artificial hip joint may also be dislocated. It is sometimes dislocated after an injury but can occur while people are doing their usual daily activities, even when crossing their legs.

[Magaret]

Most hip dislocations are posterior and result from severe posteriorly directed force to the knee while the knee and hip are flexed (eg, against a car dashboard).
(See Overview of Dislocations.)
Complications may include

Sciatic nerve injury
Delayed osteonecrosis of the femoral head

Associated injuries include

Patella fractures
Posterior cruciate ligament injuries
Acetabular and femoral head fractures

In patients with posterior dislocations, the leg is shortened, adducted, and internally rotated. Anterior dislocations are rare and result in the leg being abducted and externally rotated.