Collins English Dictionary
1. the act of displacing or the state of being displaced; disruption.
2. (esp. of the bones in a joint) the state or condition of being dislocated.
3. a line, plane, or region in which there is a discontinuity in the regularity of a crystal lattice.
4. Geology a less common word for fault (6).
Displacement of bones meeting at a joint. It causes pain, swelling, loss of function, and deformity. It is usually due to an accident, but may be caused by disease or be congential (occurring before birth). Treatment is by manipulation, which may require a local or general anaesthetic.
The shoulder and elbow are common sites of dislocation. There may be associated fractures.
Dislocations may be partial or complete. They are classified as "simple" when the skin is unbroken, and "compound" when the displaced bone pierces the skin. A complicated dislocation is a displacement of a bone, accompanied by severe local damage to the soft parts, or fracture of the bone. The process of righting a dislocation is called "reduction". There is a congenital form of dislocation of the hip in which the head of the femur (thigh-bone) on one or both sides is not seated in its proper position in relation to the pelvis. This is due to faulty growth and not to injury. It occurs more frequently in girls than in boys, and soon after birth can be detected by a "clicking" in the affected hip. Treatment consists of splinting the limb in a position which allows the head of the femur to seat properly in the pelvis. Congenital hip dislocation may not be noticed until the child starts to walk, at which time the deformity becomes obvious as a limp or waddling gait. Surgery may be required to correct it. Left alone, such hips eventually develop marked osteoarthritis.