The cause of pain at the joint between the arm and the shoulder may be frozen shoulder, rotator cuff injury, chronic strain injury, shoulder dislocation and so on. 1. Frozen shoulder: degenerative changes in the shoulder joint and its surrounding soft tissues produce aseptic inflammation, leading to pain at the joint between the arm and the shoulder. 2. Rotator cuff injury: due to acute trauma or multiple chronic injuries, the rotator cuff ruptures, leading to swelling of the shoulder joint, producing aseptic inflammation, which in turn causes pain. 3. Chronic strain injury: Maintaining the posture of working at a desk for a long time or sitting in an incorrect posture leads to excessive fatigue and stiffness of the muscles around the shoulder, which affects blood circulation and causes pain at the joint of the arm and the shoulder. 4. Shoulder dislocation: dislocation caused by trauma or habitual dislocation will lead to shoulder pain, swelling and restricted movement. Cervical spondylosis, cold and other factors can also cause pain in the arm-shoulder joint. When symptoms of pain in the arm-shoulder joint appear, you should go to the hospital in time for examination and symptomatic treatment according to the cause.