The hip is a ball-and-socket joint, which gives it a great deal of stability and allows it to move freely. The round head of the thighbone (femur) fits inside a cup-shaped socket (acetabulum) in the hipbone (pelvis). It requires substantial force to pop the thighbone out of its socket. But that's just what happens in a hip dislocation.

Causes
Motor vehicle accidents are the most common cause of hip dislocations, but wearing a seatbelt can reduce your risk substantially. A fall from a ladder or an industrial accident can also generate enough force to dislocate a hip. Someone with a dislocated hip will often have other injuries, including fractures in the pelvis and legs, back injuries or head injuries.

Symptoms
In nine out of ten hip dislocations, the head of the thighbone is pushed out and back (posterior dislocation). This leaves the hip in a fixed position, bent and twisted in towards the middle of the body. If the thighbone slips out and forward (anterior dislocation), the hip will be only slightly bent and the leg will twist out and away from the middle of the body. A hip dislocation is very painful; the patient is unable to move the leg and, if there is nerve damage, may not have any feeling in the foot or ankle area.

Treatment
If there are no other complications, the physician will administer an anesthetic or a sedative and manipulate the bones back into their proper position. If there are complications, the bones can be adjusted during surgery. Afterwards, the surgeon will request another set of X-rays and possibly a CT (computed tomography) scan to ensure that the bones are in the proper position.

It takes time - sometimes as long as two to three months - for the hip to heal after a dislocation. The orthopedic surgeon may recommend traction for a short period, followed by controlled exercises using a continuous-passive-motion machine. The patient can probably begin walking with crutches when he or she is free of pain, and should continue to use a walking aid, such as a cane, until the limp disappears.

A hip dislocation can have long-term consequences. As the thighbone is pushed out of its socket, it can disrupt blood vessels and nerve functioning. This can result in some tissue death. The protective cartilage covering the bone may also be damaged, increasing the risk of developing arthritis in the joint.