Scapular winging is the medical term for a shoulder blade (scapula) visibly protruding from the back. This occurs when the shoulder blade, or scapula, fails to lie flat against the rib cage. This abnormal positioning makes the bone appear to stick out, particularly during certain movements like pushing or reaching. Scapular winging is the visible result of a mechanical issue in the muscles or nerves that stabilize the shoulder. Understanding the underlying cause determines the appropriate path to recovery.
Muscle Imbalances and Mechanical Causes
The majority of scapular winging cases result from a breakdown in the mechanical coordination of the muscles that anchor the shoulder blade to the thoracic wall. The most common muscular culprit is weakness in the serratus anterior, a muscle that holds the scapula flush against the chest wall during arm movement. When this muscle is weak or fatigued, the medial border of the scapula lifts off the back, creating a noticeable protrusion often described as “medial winging.”
This weakness can develop due to poor posture, which chronically overstretches the muscle, or from repetitive strain activities. Athletes involved in overhead sports or individuals with jobs requiring frequent reaching can experience this overuse. The constant stress gradually compromises the muscle’s strength and endurance, disrupting the smooth, synchronized motion required between the shoulder blade and the upper arm.
Other mechanical imbalances involve the rhomboids and the trapezius. The rhomboids pull the shoulder blade inward toward the spine, and weakness allows the scapula to move excessively away from the center line. Weakness in the trapezius muscle, which stabilizes, elevates, and rotates the scapula, can also lead to improper positioning. This muscular imbalance, often termed scapular dyskinesis, means the scapula is moving improperly, which places abnormal stress on the entire shoulder complex and frequently causes pain.
The Role of Nerve Damage
Muscle weakness can be a secondary symptom of a problem in the nerves that deliver signals to those muscles. When a nerve is injured, compressed, or inflamed, it cannot transmit the necessary signal, leading to the muscle becoming paralyzed or profoundly weakened. The specific location of the winging often points directly to the affected nerve.
Winging caused by serratus anterior paralysis, the most common form, results from damage to the long thoracic nerve. This nerve is susceptible to traction injuries from sudden, forceful movements or repetitive stretch injuries common in athletics. Compression from blunt trauma, or inflammation following a viral illness, can also impair the long thoracic nerve’s function, leading to the prominent medial winging.
The two other nerves involved are the dorsal scapular nerve and the spinal accessory nerve. The dorsal scapular nerve controls the rhomboid muscles, and its impairment typically causes a more subtle winging, where the inferior angle of the scapula rotates laterally. Damage to the spinal accessory nerve, which controls the trapezius muscle, often results in lateral winging, where the outer edge of the shoulder blade sticks out.
When to Seek Professional Evaluation
If you notice a sudden, pronounced protrusion of your shoulder blade, especially if it is accompanied by pain, weakness, or an inability to lift your arm, a professional evaluation is warranted. A healthcare provider will typically begin with a detailed physical examination, observing the scapula’s position at rest and its movement during specific tasks like pushing against a wall or raising the arm overhead. This visual assessment helps to classify the type of winging and identify the likely affected muscle group.
To confirm a neurological cause and pinpoint the exact location of the nerve impairment, a physician may recommend electrodiagnostic studies, such as electromyography (EMG) and nerve conduction studies (NCS). These tests measure the electrical activity in the muscles and the speed of signal transmission along the nerves. Imaging like X-rays or magnetic resonance imaging (MRI) may also be used to rule out structural causes, such as bone tumors or fractures, and to assess soft tissue damage.
Treatment depends entirely on the underlying cause identified through diagnosis. For cases stemming from muscle weakness or mild nerve irritation, the initial approach is overwhelmingly conservative. This involves a course of physical therapy focused on strengthening the surrounding scapular stabilizers to improve shoulder mechanics. Recovery for nerve-related winging can be lengthy, sometimes taking up to 18 to 24 months, as nerves heal slowly. Surgical intervention, such as nerve transfers or muscle transfers, is typically reserved for severe cases where conservative treatment has failed to restore function after a significant period.