Scapular winging happens when the shoulder blade lifts away from the ribcage instead of sitting flat against it. The cause is almost always a problem with one of three nerves that control the muscles holding your scapula in place, though bony growths and joint conditions can also be responsible. Understanding which nerve or structure is involved matters because it determines both how the winging looks and how it’s treated.
How the Scapula Stays in Place
Your scapula isn’t connected to your spine by any joint. It’s held against your back entirely by muscles, which is why it can move so freely when you reach, lift, or rotate your arm. Three muscles do most of the stabilizing work: the serratus anterior (which wraps around your ribs under your armpit), the trapezius (the large diamond-shaped muscle across your upper back), and the rhomboids (which connect your scapula to your spine). Each of these muscles is controlled by a different nerve, and damage to any one of them can cause the scapula to wing outward.
Researchers classify scapular winging into four types based on the underlying structure involved: nerve pathology (the most common), muscle pathology, bony causes, and joint disease.
Long Thoracic Nerve and the Serratus Anterior
The single most common cause of scapular winging is injury to the long thoracic nerve, which powers the serratus anterior muscle. When this nerve stops working, the serratus anterior can no longer pull your scapula forward and flat against the ribcage. The result is medial winging, where the inner border of the scapula (the edge closest to your spine) lifts away from your back. This becomes most obvious when you push against a wall or reach your arm forward.
The long thoracic nerve is unusually vulnerable to injury because of its anatomy. It runs a long, relatively unprotected course along the side of your chest. That length makes it susceptible to being stretched, compressed, or nicked during certain activities and medical procedures. Specific surgeries that can damage it include mastectomy with lymph node removal, first rib resection, chest tube placement, and internal jugular vein cannulation. Iatrogenic damage (injury during medical procedures) accounts for roughly 11% of serratus anterior paralysis cases, and sometimes the cause is simply how a patient was positioned on the operating table.
Despite being the best-known cause of winging, serratus anterior palsy is genuinely rare. One electromyography lab found just 15 cases among 7,000 patients, and the Mayo Clinic once identified only a single case out of 38,500 patients. That said, some orthopedic groups have called it a “fairly common entity,” with one university hospital system seeing 10 cases in three years, suggesting it may be underdiagnosed.
Spinal Accessory Nerve and the Trapezius
Injury to the spinal accessory nerve paralyzes the trapezius muscle and produces a different pattern called lateral winging. Instead of the inner border lifting up, the entire scapula shifts downward and the bottom corner rotates outward. This type of winging is most noticeable when you try to raise your arm to the side.
The spinal accessory nerve is particularly at risk during surgeries or biopsies in the neck, especially procedures involving the posterior triangle (the area behind the large neck muscle you can feel when you turn your head). Published incidence data for trapezius-related winging is scarce, reflecting how rarely it’s formally documented.
Dorsal Scapular Nerve and the Rhomboids
The third nerve involved is the dorsal scapular nerve, which controls the rhomboid major, rhomboid minor, and levator scapulae muscles. These muscles pull your scapula toward your spine and hold it firmly against your back. When the dorsal scapular nerve is damaged, weakened rhomboids allow the scapula to flare out posteriorly, producing a milder but still noticeable winging.
The most common source of rhomboid paralysis is entrapment of the dorsal scapular nerve as it passes through the middle scalene muscle in the neck. Over time, chronic entrapment leads to muscle atrophy and denervation, making the winging progressively worse. No published data exists on how frequently this occurs, likely because it’s often missed or attributed to other shoulder problems.
Sports and Repetitive Strain
Athletic activity is a well-documented trigger, particularly for long thoracic nerve injuries. The mechanism is usually a stretch or traction injury to the nerve during vigorous overhead or rotational movements. Sports specifically linked to long thoracic nerve damage include baseball, tennis, golf, and weightlifting. Patients typically develop shoulder pain or dysfunction after either a single acute event or a period of intense training, followed by visible scapular winging consistent with serratus anterior weakness.
The pattern makes sense given the nerve’s anatomy. Any forceful motion that pulls the shoulder forward and down, or involves repetitive overhead reaching, can tug the long thoracic nerve beyond what it can tolerate. This is why it sometimes appears in people who’ve done nothing more unusual than heavy yard work or an aggressive weekend workout.
Bony Growths and Structural Causes
Not all winging comes from nerve damage. Bony growths on the underside of the scapula, most commonly osteochondromas (benign cartilage-capped bone tumors), can physically push the scapula away from the ribcage. This produces what’s sometimes called pseudowinging or static winging, because the scapula sticks out at rest and doesn’t change much with movement. That’s a key difference from nerve-related winging, which typically worsens during specific motions.
Osteochondromas are the most common tumor of the scapula, though scapular involvement overall is rare. They’re usually painless unless they cause complications like mechanical restriction of shoulder movement, fracture of the tumor’s bony stalk, nerve compression, or formation of a fluid-filled sac. A telltale sign is a grating or snapping sensation when you internally rotate your shoulder, and audible crepitus (a crackling sound) with certain arm movements. Diagnosis usually requires a CT scan or lateral X-ray, since standard front-to-back X-rays can miss growths on the scapula’s undersurface.
Neuralgic Amyotrophy
One cause that deserves separate mention is neuralgic amyotrophy (also called Parsonage-Turner syndrome), an inflammatory condition that attacks the nerves of the shoulder. It typically begins with sudden, severe shoulder pain that fades over days to weeks, followed by weakness and wasting of the affected muscles. It’s one of the more common causes of scapular winging, and electromyography shows abnormalities in over 95% of cases. The condition can affect the long thoracic nerve, the spinal accessory nerve, or other shoulder nerves, so the pattern of winging varies.
How Doctors Tell the Causes Apart
The first step is a physical exam. The classic test is the wall push-up: you place your hands against a wall and push while a clinician watches your scapula from behind. If the inner border lifts off, it suggests serratus anterior weakness. However, recent research has shown this test is far less specific than previously thought. In one study of 50 patients, every single one showed increased scapular winging during the wall push-up, but 45 of those were false positives for serratus anterior dysfunction. The test was 100% sensitive (it never missed a true case) but 0% specific (it couldn’t distinguish serratus anterior problems from other causes of abnormal scapular movement).
A newer test called the shoulder flexion resistance test, where a clinician resists your arm moving forward at various angles with your elbow straight, performed dramatically better. It was 100% sensitive and 100% specific for serratus anterior dysfunction. The difference matters because accurate identification of the cause determines whether surgical intervention is appropriate.
Electromyography (needle EMG) is the standard tool for confirming which nerve is involved. Its sensitivity ranges from 50% to 91% and specificity from 87% to 97% for neuromuscular disorders in general. When bony causes are suspected, imaging with CT or MRI is used, with MRI being especially useful for measuring the cartilage cap of an osteochondroma to assess whether it’s benign.
Recovery Timelines
When winging results from nerve injury, recovery depends on how severely the nerve was damaged. In cases involving both the nerve’s insulation (myelin) and the nerve fiber itself, recovery takes several weeks to months as the nerve slowly regenerates. Physical therapy is the standard first-line approach, but the literature is mixed on whether therapy alone is sufficient for significant nerve injuries. Some patients recover fully with conservative treatment, while others plateau and require surgical options like nerve release or muscle transfer.
The unpredictability of recovery is one reason accurate diagnosis matters early. Identifying the specific nerve, the severity of damage, and whether the cause is ongoing (like nerve entrapment) versus a one-time event (like a surgical injury or stretch) shapes realistic expectations for how long recovery will take and whether intervention might speed it along.