Prevalence: A Common Movement, Not a Rare Disorder
Far from being a rare condition, how rare is scapular dyskinesis? The answer is that it's not rare at all. Systematic reviews of scientific literature have shown that this abnormal motion of the shoulder blade is quite prevalent. A comprehensive review published in 2023 indicated that approximately 48% of asymptomatic individuals—people with no current shoulder pain—display signs of scapular dyskinesis. The numbers are even higher among those with existing shoulder injuries or pain, with prevalence ranging from 57% to a staggering 81% depending on the specific group and study. In athletic populations, especially overhead athletes, the prevalence can be as high as 100% in symptomatic cases. This high incidence suggests that scapular dyskinesis is a common functional impairment, challenging the notion of it being an uncommon clinical finding.
Prevalence Comparison
To better understand the frequency of scapular dyskinesis, consider these findings from research:
- Asymptomatic General Population: A study in 2023 revealed a prevalence of 59% in this group.
- Asymptomatic Athletes: Studies show rates of approximately 42%.
- Symptomatic General Orthopedic Population: Individuals with shoulder pain see rates of 57%.
- Symptomatic Athletes: The highest prevalence is found here, with rates up to 81%.
What Exactly is Scapular Dyskinesis?
Scapular dyskinesis refers to the loss of proper control over the motion and position of the scapula during shoulder movements. Rather than a specific injury or diagnosis, it is best understood as a physical impairment—a dysfunctional movement pattern. The scapula is a key component of the shoulder's kinetic chain, acting as a stable base for the arm. When this base moves incorrectly, it affects the entire shoulder complex. Signs of dyskinesis can include:
- Visible 'Winging': The medial border of the shoulder blade protrudes excessively from the back.
- Early Elevation: The shoulder shrugs or elevates too soon during arm movement.
- Rapid Downward Rotation: The scapula drops too quickly as the arm is lowered.
These signs can be subtle or dramatic and are often most noticeable during the downward phase of arm elevation.
Common Causes and Associated Conditions
While scapular dyskinesis is a movement pattern, it doesn't happen in a vacuum. It almost always stems from underlying issues. Causes can be broadly categorized into several groups:
- Shoulder-Related Issues: A wide range of shoulder pathologies are associated with dyskinesis. These include rotator cuff injuries, shoulder impingement syndrome, glenohumeral instability, and labral tears.
- Muscle Imbalance and Weakness: The muscles that control the scapula, such as the serratus anterior and trapezius, can become imbalanced, weak, or fatigued. This can disrupt the delicate timing and force required for proper scapular movement.
- Posture: Poor posture, such as a rounded or 'slouched' upper back (thoracic kyphosis), can alter the resting position of the scapula and affect its movement.
- Nerve Damage: Though less common than muscular issues, damage to nerves like the long thoracic nerve can cause significant scapular winging.
- Injuries: Previous or acute injuries to the clavicle, acromioclavicular (AC) joint, or the scapula itself can lead to compensatory movement patterns and resulting dyskinesis.
Diagnosing Scapular Dyskinesis
The most effective way to diagnose scapular dyskinesis is through visual observation during a physical examination by a healthcare professional. Unlike many orthopedic conditions, X-rays or MRIs are typically not required to identify the movement pattern itself, though they may be used to uncover underlying shoulder pathologies. A clinician may perform specific tests to confirm the impairment:
- Scapular Dyskinesis Test: The patient is asked to raise and lower their arms several times, often while holding a light weight, allowing the clinician to observe the scapular motion.
- Scapular Assistance Test (SAT): The examiner manually assists the scapula during arm movement. If this assistance improves function and reduces symptoms, it points toward a scapular muscular issue.
- Scapular Retraction Test: Manual resistance is applied to the arm, first in a normal posture and then while the scapula is manually stabilized. An increase in strength with stabilization indicates dyskinesis.
A Comparison of Symptomatic vs. Asymptomatic Individuals
The presence of scapular dyskinesis varies significantly based on whether an individual is experiencing symptoms, but it is a common finding across the board. The following table highlights the difference, based on a 2023 systematic review:
| Population Group | With Scapular Dyskinesis | Without Scapular Dyskinesis |
|---|---|---|
| Asymptomatic Athletes | 42% | 58% |
| Asymptomatic General Population | 59% | 41% |
| Symptomatic Athletes | 81% | 19% |
| Symptomatic General Orthopedic Population | 57% | 43% |
Treatment and Long-Term Prognosis
Rehabilitation for scapular dyskinesis focuses on correcting the underlying cause rather than just the visible movement. A physical therapist will often employ a multifaceted approach, emphasizing motor control over isolated strength gains. Treatment strategies include:
- Addressing Mobility Issues: Stretching tight muscles, such as the pectoralis minor, to allow the scapula to move more freely.
- Improving Motor Control: Exercises that help retrain the neuromuscular patterns involved in shoulder movement, such as wall rollouts or specific core exercises that integrate with shoulder function.
- Strengthening Scapular Stabilizers: Targeting weakened muscles, including the serratus anterior and lower trapezius, with progressive exercises.
- Integration of the Kinetic Chain: Ensuring that the hips, trunk, and legs are all working together with the shoulder to create coordinated, efficient movement.
The long-term prognosis for scapular dyskinesis is generally favorable, especially with proper rehabilitation. For asymptomatic athletes, research indicates that the presence of dyskinesis increases the risk of future shoulder pain by 43%. This makes early detection and proactive intervention a valuable strategy. Ignoring the issue, however, can lead to potential complications, including chronic pain, inflammation, shoulder stiffness, or rotator cuff tears over time. Therefore, treating the underlying impairment is crucial for maintaining long-term shoulder health.
For more in-depth information on the complexities of this condition, visit the National Institutes of Health research archives, where you can find multiple studies on the topic: https://www.ncbi.nlm.nih.gov/
Conclusion
Scapular dyskinesis is a common impairment, not a rare condition, present in nearly half of people without shoulder pain. Its prevalence increases significantly in those with shoulder injuries, particularly overhead athletes. As a physical impairment rather than a diagnosis, it typically results from underlying issues such as muscle imbalances, poor posture, or other shoulder pathologies. While it can be a precursor to future shoulder pain, proper diagnosis through physical examination and a comprehensive rehabilitation program focusing on motor control and muscle balance can effectively manage the condition and improve long-term outcomes. Awareness of this surprisingly common movement pattern is the first step toward better shoulder health and injury prevention.
