The bending part of the arm is called the elbow joint, which is composed of the distal humerus and the proximal ends of the ulna and radius, and is a compound joint, which includes three joints, the humeral-ulnar joint, the humeral-radial joint, and the proximal humeral-ulnar joint, and the three joints are together encased in a joint capsule. The anterior and posterior walls of the elbow capsule are weak and lax, while the walls on both sides are thick and tense and are reinforced by lateral collateral ligaments. The posterior wall of the capsule is the weakest, and after trauma, the radius and ulna are easily dislocated posteriorly and move to the posterior top of the humerus, resulting in a local dislocation deformity. The diagnosis can be confirmed by radiographs and physical examination, and can be repositioned by manipulation. The elbow joint is prone to trauma and degeneration, so it is important to strengthen the muscles and protect the elbow joint during normal life.