Left shoulder blade pain has many causes. According to the U.S. National Library of Medicine and the National Institutes of Health, or NIH, the shoulder is one of the body's more unstable joints, and it's the site of many common problems. The shoulder blade or scapula can also experience problems. Pain may arise in the shoulder blade itself, or it can be referred from another part of the body, such as the lungs.
A scapula fracture can cause left shoulder blade pain. According to the American Academy of Orthopaedic Surgeons or AAOS, scapula fractures account for less than 1 percent of all broken bones. Although scapula fractures are rare, they can be extremely painful and are often accompanied by other traumatic injuries, such as rib fractures, concussions, punctured lungs and spinal cord damage. The AAOS states that the most common cause of scapula fractures is high-energy, blunt-force trauma, which is the type of injury that can occur in a motor vehicle accident. Common signs and symptoms associated with a scapula fracture include severe pain when moving the affected-side arm, shoulder swelling and skin abrasions. According to the AAOS, if left untreated, a scapula fracture can cause chronic shoulder pain and shoulder dysfunction. The body of the scapula is the portion of the bone most commonly fractured, accounting for 50 to 60 percent of scapula fractures.
A Pancoast tumor can cause left shoulder blade pain. The National Cancer Institute or NCI--a division of the National Institutes of Health--states that a Pancoast tumor, also known as a sulcus tumor, is a type of lung cancer that manifests in the lung's upper lobes and can spread to neighboring tissues, including the ribs and the vertebrae. According to the NCI, the majority of Pancoast tumors are non-small cell lung carcinomas. The Pancoast Tumor website states that Pancoast tumors are generally malignant, develop in the lung's upper lobes, grow into a large mass, invade the chest wall and other nearby structures and destroy shoulder and neck nerves. One of the most common causes of Pancoast tumors is smoking. Common signs and symptoms associated with a Pancoast tumor--especially among smokers--include chest pain, shoulder pain and upper back pain.
A subscapularis muscle strain can cause left shoulder blade pain. According to the Sports Injury Clinic website, the subscapularis muscle runs from the underside of the scapula to the front of the upper arm. The subscapularis muscle is responsible for rotating the arm inward and is one of four rotator cuff muscles. Athletes participating in throwing sports may experience a subscapularis strain--micro-tears in the muscle fibers--and shoulder blade pain. The Sports Injury Clinic website notes that partial ruptures of the subscapularis muscle are more common than complete ruptures, although the partial rupture may cause significant inflammation in the affected area. Common signs and symptoms associated with a subscapularis strain include pain with overhead shoulder movements, pain when the affected-side arm is rotated inward against resistance and pain when the muscle's tendinous is compressed at its insertion point on the humerus or upper arm bone.