The scapula acts as the foundation for the entire shoulder joint, providing a stable yet mobile base from which the arm moves. Proper function of this triangular bone is achieved through highly coordinated movement with the upper arm bone (humerus). When this coordination breaks down, the altered or improper motion is described as scapular dyskinesis (SD). This impairment is not a diagnosis, but rather a sign that the underlying mechanics of the shoulder complex are compromised. Scapular dyskinesis is a common finding in many people with shoulder pain and dysfunction, signaling an issue that must be addressed for full recovery.
What Is Scapular Dyskinesis?
The term scapular dyskinesis describes a loss of control over the shoulder blade’s normal movement and position. A healthy shoulder exhibits what is known as the scapulohumeral rhythm, which is the precise, integrated motion between the scapula and the humerus during arm elevation. This rhythm typically involves the glenohumeral joint (shoulder joint) moving twice as much as the scapulothoracic joint (shoulder blade sliding over the rib cage).
When dyskinesis occurs, this precise rhythm is compromised, resulting in asynchronous or erratic movement of the shoulder blade. The scapula may exhibit excessive prominence of its borders, a phenomenon often referred to as “winging” or “tipping.” This altered motion reduces the efficiency of the shoulder, diminishes the subacromial space, and can lead to excessive strain on surrounding tissues like the rotator cuff. Compromised stability of the scapula impairs overall shoulder function.
How Abnormal Movement Is Classified
Clinicians often classify scapular dyskinesis into distinct patterns based on the most prominent visible deviation, which helps to standardize assessment. The Kibler classification system is a common method that visually categorizes the movement abnormality into three main types. These classifications focus purely on the visual pattern of movement dysfunction during arm elevation and lowering.
Type I dyskinesis is characterized by the prominence of the inferior angle of the scapula, meaning the bottom tip of the shoulder blade sticks out from the back. Type II presents with the entire medial border of the scapula lifting away from the rib cage, which is the classic “winging” appearance. This visual cue indicates abnormal rotation around a vertical axis.
Type III is identified by the superior border of the scapula being visibly prominent or elevated, suggesting excessive superior translation of the entire bone. This movement pattern is often associated with compensatory shrugging or early elevation during arm movement.
Common Factors That Lead to Dyskinesis
Scapular dyskinesis is rarely a standalone condition and typically results from an underlying mechanical or neurological issue. The most frequent cause is muscle imbalance, specifically involving the muscles that control the shoulder blade’s position on the rib cage. Weakness or fatigue in the serratus anterior and the lower trapezius muscles is a common finding, as these muscles are responsible for holding the scapula flat and rotating it upward during arm movement.
The weakness of these stabilizers is often combined with tightness in opposing muscle groups, such as the pectoralis minor, which can pull the scapula into an anteriorly tilted and protracted position. Postural factors, like an increased rounding of the upper back (thoracic kyphosis), also contribute by altering the resting position of the scapula and inhibiting the function of the stabilizing muscles.
In a small percentage of cases, nerve injury is the direct cause of muscle paralysis and subsequent dyskinesis. Damage to the long thoracic nerve leads to paralysis of the serratus anterior, resulting in medial border prominence or winging. Other contributing factors include injuries to the shoulder joint itself, such as rotator cuff tears or acromioclavicular joint separation, which secondarily affect scapular mechanics.
Management and Rehabilitation Strategies
Treatment for scapular dyskinesis focuses on correcting the underlying factors and restoring the normal, coordinated movement patterns of the shoulder blade. The initial phase of management typically involves reducing associated pain and inflammation through activity modification. Once pain is controlled, the focus shifts to improving the flexibility of tight structures, such as the pectoralis minor and posterior rotator cuff muscles.
Core rehabilitation strategies center on targeted strengthening of the scapular stabilizing muscles, particularly the serratus anterior and the lower and middle trapezius. Exercises are often initiated in low-load positions, such as closed kinetic chain activities like weight shifting or wall push-ups, to ensure the shoulder blade is properly controlled. These exercises are designed to re-educate the muscles on their proper activation timing and sequence, which is often described as a motor control issue rather than a simple strength deficit.
Postural correction is a simultaneous element of rehabilitation, addressing issues like forward head and rounded shoulders to provide a better foundation for the scapula. The overall goal is to progress the exercises from isolated muscle activation to dynamic activities that integrate the scapula with the arm and the rest of the body’s kinetic chain. Consistent practice is necessary to retrain the nervous system and achieve a lasting change in shoulder mechanics.