There are three special signs of joint dislocation, which are as follows: 1. deformity: after joint dislocation, the joint alignment relationship is abnormal, the joint morphology is significantly changed, and there is a deformity of limb shortening or lengthening; 2. elastic fixation: the injured limb is kept in a specific position where both active and passive movements are restricted, such as a spring, and there is resistance when it is plucked, and after the passive force is removed, it returns to its original position; 3. pelvic void: the joint head leaves its original position, thus causing the pelvis to be empty.