When the arm hurts when you lift it after a fall, there are several possible causes: 1. Local soft tissue contusions or ligament strains in the arm, usually manifesting as local swelling and pain, but generally no obvious deformity. If the arm is lifted with force, the injured muscles or ligaments must be exerted, and pain will occur. 2. If there is no very obvious deformity, it may be a crack fracture. If the local deformity is obvious and there is longitudinal percussion pain when moving passively, the fracture is highly suspected and the diagnosis can be basically confirmed by going to the hospital to check the X-ray.