Pain anywhere in the body is a sign, like the "check engine" light going off in a vehicle, which indicates that there is something wrong. The amount of pain does not indicate the severity of the problem. Pain under the left shoulder can be from mild cause like a muscle injury to more serious problems like a heart attack or internal bleeding.
Subscapularis Injury
Four muscles make up the rotator cuff. The subscapularis muscle is located under the shoulder blade. Trauma or repetitive overuse injury can cause this muscle to tear or spasm. Being located where it is, it is often a hard muscle to reach and massage. Chiropractors, physical and massage therapist can use their hands or other tools to access the area under the scapulae to work out the muscle tightness and tenderness.
Trigger Points
Trigger points are also known as "knots" and feel like a hard and tender lump of tissue with in the muscle. Trigger points are made of muscle that has gone into spasm from overuse and the waste products the muscle produces. According to "Trigger Point Therapy for Myofascial Pain: The Practice of Informed Touch," trigger points in the neck and upper traps can refer into, behind and around the shoulder joint as well as all the way down the arm.
Fractured Scapula
Fracturing the scapula is a rare occurrence; it is the least fractured bone in the body, accounting for only 1 percent of body fractures, according to the American Academy of Orthopedic Surgeons. A fracture to this area is caused by high force blunt trauma like a motorcycle or auto accident. Intense pain will be felt at the back of the shoulder, both on top and below the shoulder blade. Without treatment, the injured scapula may cause chronic and permanent pain in and around the shoulder.
Other Causes
Many internal organs do not have their own pain nerves. These nerves are shared with other areas of the body, so an injury or irritation to an organ like the stomach may share or refer pain to the left shoulder blade. The National Institutes of Health indicate that pain in any of the abdominal organs can refer pain to one shoulder or another, or just centrally between the shoulder blades. A combination of abdominal pain and pain between or to one shoulder is considered an emergency situation.
Chest Pain
Any time there is a combination of chest pain and referred pain to the left shoulder, arm or jaw, there is a concern of a heart attack. Heart attacks can happen without causing any referred pain, but the National Institutes of Health say to call 911 if there is pain between the shoulders or referring to the left side, combined with chest tightness or shortness of breath.
References
- "Trigger Point Therapy for Myofascial Pain: The Practice of Informed Touch"; Donna Finando L.Ac. L.M.T and Steven Finando Ph.D. L.Ac.; 2005
- AAOS: Scapula Fracture
- NIH: Abdominal Pain
- NIH: Chest Pain
