Possible causes of arm pain and inability to move backward include muscle strain, frozen shoulder, rotator cuff injury, and so on. 1. Muscle strain: it may be due to excessive muscle contraction or stretching, more than its tolerance, resulting in muscle strain, resulting in pain and swelling of the arm muscles, and restricted movement can not go backward phenomenon. 2. Frozen shoulder: it may be caused by chronic inflammation and fibrosis of the joint capsule and surrounding ligamentous tissues, resulting in frozen shoulder, and also symptoms such as pain around the shoulder joint and limited activities. 3. Rotator cuff injury: rotator cuff injury caused by trauma, repetitive motion and degenerative lesions, and there will also be symptoms such as shoulder pain, localized swelling and activity limitation. There may be other reasons for arm pain, it is recommended to go to the hospital in a timely manner to improve the examination, to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.