Pain in the left back and arm area may be related to left back soft tissue strain, angina pectoris, frozen shoulder and so on. 1. Soft tissue strain of the left back: due to activities, excessive exercise of the left upper limb, after physical labor, there is inflammation of the fascia around the shoulder joint, muscle strain, and then the left arm as well as the back of the soreness, distension, and sometimes tingling. 2. Angina pectoris: often induced by exertion, temporary ischemia of the heart muscle causes an attack of chest pain or chest tightness discomfort, resulting in pain in the precordial area, and there may be radiating pain in the left back and arm area. 3. Frozen shoulder: due to chronic injury caused by long-term over-activity and poor posture, degenerative changes occur in the shoulder joint and its surrounding soft tissues, resulting in inflammation around the shoulder joint. Inflammation causes pain in the shoulder joint, which can spread to the back of the shoulder and the upper and middle parts of the arm, and sometimes reaches the surface of the flexor muscles of the forearm. When pain in the left back and arm area occurs, it is recommended to consult a doctor for further examination, to clarify the cause with the help of the doctor, and to carry out targeted treatment or therapy.