There are three main causes of back pain below the right shoulder: 1. The strain of the infraspinatus and teres minor muscles below the right shoulder, such as the external rotation of the shoulder joint when lifting and carrying heavy objects, can cause the infraspinatus and teres minor muscles to contract violently. If the normal load of the muscles is exceeded, a strain will occur, resulting in localized tissue damage, inflammatory edema and bruising and swelling, and painful stimulation of the peripheral nerves. 2. The strain is caused by the infraspinatus and teres minor muscles, such as frequent external rotation of the shoulder joint. This can lead to continuous muscle contraction, resulting in fatigue or strain and the formation of localized sterile inflammatory lesions that can stimulate peripheral nerves and cause pain. 3. The muscles in this location become tense after exposure to cold, resulting in decreased local arterial blood supply, decreased electrolyte, energy and nutritional support, and slowed venous return. The lactic acid and metabolic products formed in this way cannot be metabolized in a timely and effective manner and accumulate, stimulating the peripheral nerves and causing pain in this location.