Back shoulder blade and underarm pain may be caused by strenuous exercise, cervical spondylosis, fasciitis and other reasons. 1. Strenuous exercise: it may be the shoulders, arms and other parts of the body, a large number of activities, such as jumping rope, jumping drill, etc., can make a large accumulation of lactic acid, which can appear back shoulder blade and underarm pain. 2. Cervical spondylosis: degenerative changes in the cervical intervertebral discs lead to imbalance in the balance between the soft tissues of the neck and the dynamic and static forces of the vertebral body, resulting in intervertebral disc abnormalities, which leads to a series of symptoms and signs. When suffering from neurogenic cervical spondylosis, pain in the shoulder and the medial border of the scapula can occur, and it can also radiate to the axilla, which can cause pain in the scapula and axilla in the back. 3. Fasciitis: it refers to the pathological changes in the fascia and causes various uncomfortable symptoms in the myofascia of the body, which may be caused by the body being subjected to cold, damp climate environment, trauma and other reasons. When fasciitis occurs in the scapula and axilla of the back, pain can occur due to the stimulation of inflammation. Pain in the back shoulder blades and armpits may also be caused by other reasons, such as cardiovascular disease, etc. Patients are advised to go to the hospital in time and follow the doctor’s instructions for treatment to avoid delays.