Left subscapularis pain may be caused by muscle strain, shoulder joint inflammation, heart disease, shingles and other reasons. 1. Muscle strain: long-term weight-bearing or heavy activities of the muscles at the left scapula may cause local muscle strain or strain injury, resulting in subscapularis pain. 2. Inflammation of shoulder joint: In patients with frozen shoulder, adhesive pain around the shoulder joint caused by aseptic inflammation may also manifest as pain under the left scapula. 3. Heart disease: Certain heart diseases, which can also manifest as referred pain in the left shoulder, are easily overlooked or misdiagnosed. 4. Herpes zoster: A small number of patients with herpes zoster can present with pain in the left shoulder blade in the early stages. The pain is usually persistent and pronounced. There are many other causes of left subscapularis pain, persistent subscapularis pain should be consulted as soon as possible to clarify the diagnosis and treat the cause.