Scapular winging is a condition resulting from underlying instability in the shoulder complex, where the shoulder blade, or scapula, fails to stay anchored to the rib cage. The scapula’s normal function is to glide smoothly against the back of the chest wall, providing a stable base for arm movement. When this stability is compromised, the bone rotates or lifts away from the body, creating the characteristic wing-like shape. This instability can lead to pain, stiffness, and difficulty performing daily activities that require lifting or reaching overhead.
Understanding Scapular Winging
Scapular winging is fundamentally a breakdown in the coordinated movement between the shoulder blade and the thoracic cage. The scapula is not attached to the rib cage by a fixed joint but is instead held in place and controlled by several large muscles. This muscular attachment creates a kind of suction mechanism that allows the bone to glide smoothly and remain flush against the back. The position of the scapula is extremely important because it provides the socket for the arm bone, meaning its stability directly impacts the efficiency and range of motion of the shoulder joint.
The collective action of the muscles surrounding the scapula ensures that for every three degrees of arm movement, one degree comes from the scapula rotating and two degrees come from the shoulder joint itself. When these muscles become weak or paralyzed, they can no longer maintain the necessary tension to keep the scapula against the rib cage. The winging itself can be classified based on the direction of the protrusion, most commonly seen as the medial (inner) border of the shoulder blade lifting away from the back. This abnormal movement pattern limits the ability to raise the arm above the shoulder level and can lead to muscle fatigue and discomfort.
Primary Causes of Scapular Instability
The most frequent neurological cause involves the long thoracic nerve, which supplies the serratus anterior muscle, responsible for pulling the scapula forward and anchoring its inner border. Injury to this nerve results in a paralysis of the serratus anterior, causing the inner edge of the shoulder blade to protrude, a condition known as medial winging. The long thoracic nerve can be damaged by direct trauma, such as a blunt blow to the shoulder or chest, or through repetitive traction injuries common in athletes who perform overhead movements, like weightlifters or throwers.
Damage to the spinal accessory nerve, which controls the trapezius muscle, or the dorsal scapular nerve, which supplies the rhomboid muscles, is another cause of winging. Trapezius weakness usually results in the outer border of the scapula protruding, known as lateral winging, and often causes the entire shoulder to droop. Nerve damage in these cases can be iatrogenic, meaning it is unintentionally caused by a medical procedure, such as a lymph node biopsy or neck dissection, due to the nerve’s vulnerable path through the neck.
Non-neurological causes of scapular instability also exist, often involving chronic strain or muscular imbalance. Repetitive strain from physically demanding work, poor posture, or carrying heavy shoulder bags can weaken the stabilizing muscles. In some cases, the winging may be secondary to a problem in the shoulder joint itself, such as instability or a rotator cuff tear, which forces the scapular muscles to work harder. A direct mechanical injury, such as a muscle tear or a fracture near the scapula’s attachment point, is a less common but more acute cause of instability.
Medical Diagnosis and Assessment
A healthcare professional will begin the assessment by observing the shoulder blade’s position and movement. The diagnosis is confirmed through dynamic physical tests, such as the wall push-up test, where the patient pushes against a wall; a positive result is the lifting of the scapula’s inner border. Manual muscle testing helps to pinpoint which specific muscle, like the serratus anterior or trapezius, is weakened, which in turn helps determine the likely nerve involvement.
To understand the cause more precisely, imaging and specialized nerve tests are often ordered. X-rays may be used to rule out any underlying bone fractures or structural abnormalities. Magnetic Resonance Imaging (MRI) is helpful for visualizing soft tissue, including the muscles and nearby nerves, to check for signs of inflammation or compression. The most definitive test for neurological involvement is an electromyography (EMG) and nerve conduction study, which measures the electrical activity of the muscles and the speed of nerve signals. Seeking medical attention is important if the winging is sudden, painful, or accompanied by significant arm weakness, as early diagnosis can improve treatment outcomes.
Treatment and Rehabilitation Options
Initial treatment for scapular winging typically focuses on non-surgical interventions, as many cases of nerve-related weakness, especially those involving the long thoracic nerve, resolve spontaneously. This period of spontaneous recovery can range from 6 months up to 2 years. During this period, the cornerstone of care is physical therapy, which is designed to maintain the shoulder’s range of motion and strengthen the surrounding, unaffected muscles.
A physical therapist will prescribe exercises to strengthen the weak muscles, particularly focusing on the serratus anterior and the trapezius, once signs of nerve recovery are present. Postural correction and activity modification are also implemented to reduce strain on the affected shoulder. Temporary support devices like bracing or specialized taping may be used to help stabilize the scapula during daily activities and manage discomfort, although compliance with bracing can be poor.
Surgical intervention is generally reserved for patients whose winging and functional limitations persist after a prolonged period of conservative management, usually 12 to 24 months. Options include nerve transfers, such as rerouting a healthy nerve to reinnervate the paralyzed muscle, or muscle transfers, where a functional muscle like the pectoralis major is partially moved to anchor the scapula. In severe, chronic cases where other treatments have failed, a scapulothoracic fusion, which involves surgically attaching the scapula to the rib cage, may be considered as a last resort to improve stability and pain.