An irregularity in the close positioning of the two parts of a joint that prevents the joint from functioning normally. The most common large joint dislocation occurs in the shoulder, but joint dislocations may also occur in the shoulder, hip or spinal vertebrae. Symptoms of a joint dislocation include a misshapen appearance, pain, swelling, discoloration, and an inability to move the joint. A joint that is dislocated because of trauma is a serious injury and should be treated immediately. After giving the person a muscle relaxant, the doctor will gently rotate the dislocated joint back into place. In some cases, traction or surgery may be needed.