There are several clinical reasons for pain under the left shoulder blade: 1. Frozen shoulder. If the pain worsens during left shoulder activities and leads to limited activities, this indicates that the left shoulder has a condition of frozen shoulder. This situation needs to go to the orthopedics or rehabilitation medicine department. 2. Coronary heart disease. Patients with coronary artery disease have angina pectoris, which can radiate to the left side around the shoulder blade. If it is accompanied by chest tightness, shortness of breath and discomfort in the precordial area, it needs to go to the cardiology clinic.3. Other causes. Costochondritis, intercostal neuralgia can also appear on the left side of the shoulder blade below the pain, these conditions can generally be self-healing, do not need special treatment.