A
dislocation is any displacement of a body structure from its normal position, although it is usually a misalignment of
bones at a joint. Bones are normally held together in proper alignment by tough fibrous bands called ligaments, which are attached to each bone, and by a fibrous sac called the
articular capsule, also connected to the bone. These connecting structures are relatively inelastic, but they do allow joint movement within limits. A
dislocation is usually caused by a violent movement at the joint that exceeds normal limits, tearing the ligaments and the articular capsule and throwing the bone or bones out of place. Dislocations most commonly occur at the shoulders, fingers, jaw, elbows, knees, and hips as a result of trauma, although they sometimes occur as a result of diseases that affect the joints.
In a bone dislocation the joint is immobile, and the affected limb may be locked in an abnormal position; fractures may also be present. First aid treatment consists of immobilizing the joint with a splint, sling, or bandage.