Left shoulder pain may be caused by heart disease, frozen shoulder and cervical spondylosis. 1. Heart disease: patients with coronary heart disease may suffer from angina pectoris if there is insufficient blood supply to the myocardium, which may lead to the symptom of pain in the left shoulder, which is due to the radiating pain caused by inaccurate localization of the visceral nerves, therefore, if the patients suffer from chest pain and pain in the left shoulder at the same time, the patients should be highly alert to this disease. 2. Frozen shoulder: Frozen shoulder is a kind of disease characterized by limitation of active and passive activities of the shoulder joint, which can lead to symptoms of left shoulder pain, and this disease, like heart disease, is also common in the elderly, and is related to long-term over-activity, poor posture and other factors. 3. Cervical spondylosis: Cervical spondylosis is a disease characterized by degenerative changes in the cervical intervertebral discs, which can lead to herniated discs compressing the nerve roots in the neck, thus producing symptoms of left shoulder pain. In addition to the above diseases, other diseases can also lead to symptoms of left shoulder pain. It is recommended to consult a doctor as soon as possible to find out the cause and ask the doctor to deal with it.