The shoulder blade, or scapula, is one of the largest bones in the upper body. Several muscles attach to the scapula and act as stabilizers. If these muscles do not function properly, a condition can develop in which the inside edge of the scapula sticks outward. This condition is called scapula winging and affects normal movements such as pushing, pulling, lifting and throwing.

Serratus Anterior Dysfunction

The serratus anterior, or SA, is a broad and flat muscle that originates on the ribs and attaches to the scapula. The SA holds the scapula against the thoracic wall. Muscle weakness or damage to the long thoracic nerve causes dysfunction of the SA. Blunt trauma or repetitive physical movements causes damage to this nerve. Blunt trauma can include unusual twisting of the neck and shoulder or a sudden depression of the shoulder girdle. Muscle weakness is common since the SA is not easy to strengthen with traditional movements or resistance training. SA dysfunction causes the inside edge of the scapula to stick outward, especially when the arm moves forward.

Trapezius Dysfunction

The trapezius is a large superficial muscle that originates on the thoracic spine and connects to the scapula. Its functions are to pull the scapula in toward the spine, rotate the scapula so that the topmost part of the arm faces up, move the scapula up and down, bring the head and neck in a backward direction, rotate and side bend the neck and assist in breathing. Damage to the spinal accessory nerve causes trapezius dysfunction. This is a common dysfunction since the spinal accessory nerve is located superficially and is susceptible to damage during normal movements. The lower trapezius is often weak since it is difficult to strengthen with traditional methods. Trapezius dysfunction causes the scapula to move laterally away from the spine.

Rhomboids Dysfunction

The rhomboids major and rhomboids minor are deep or interior to the trapezius. They work together to pull the scapula inward, to elevate the scapula and rotate the scapula downward. Damage to the dorsal scapular nerve causes rhomboid dysfunction. This nerve will often become entrapped. Entrapment of the dorsal scapular nerve is common among athletes who toss overhead, such as volleyball or baseball players. The rhomboids are susceptible to injury during the follow through of overhead movements, such as throwing or spiking in volleyball. Rhomboid dysfunction causes the scapula to move laterally away from the spine and rotate upward.