Scapular Dyskinesia

Introduction

• Scapular Dyskinesis (SD) refers to an alteration in normal scapular motion and positioning.

• Leads to disruption of the scapulohumeral rhythm (SHR).

• It is not a diagnosis or isolated injury, but a functional impairment.

• Commonly occurs secondary to shoulder girdle pathology.

Prevalence in Athletes

• 61% in overhead athletes (throwers, swimmers, tennis players)

• 33% in non-overhead athletes

Purpose of This Review

• Understand scapular biomechanics and anatomy

• Recognize clinical features of SD

• Learn evaluation and diagnostic methods

• Review treatment strategies

• Highlight sport-specific implications and management

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Periscapular Anatomy & Biomechanics

 

Scapular Anatomy

• Large, flat, triangular bone

• Connects the axial skeleton to the arm via:

  • Acromioclavicular (AC) joint

  • Sternoclavicular (SC) joint

• Minimal bony stability

• Highly dependent on muscular control

Primary Stabilizing Muscles

• Major muscles

  • Trapezius (upper, middle, lower)

  • Serratus anterior

  • Rhomboids

• Scapulothoracic bursae

  • Infraserratus

  • Supraserratus

  • Scapulotrapezial

  • Potential sources of pain and snapping

Functional Role

• Provides a stable base for humeral motion

• Essential for:

  • Arm elevation

  • Rotation

  • Force transfer during overhead sports

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Etiology of Scapular Dyskinesis

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Neurological Causes of Scapular Winging

• Medial winging

  • Long thoracic nerve injury

  • Serratus anterior weakness

• Lateral winging

  • Spinal accessory nerve (trapezius)

  • Dorsal scapular nerve (rhomboids)

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Kibler Classification of Scapular Dyskinesis

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SICK Scapula Syndrome

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Clinical Assessment of Scapular Dyskinesis

History

• Often gradual and insidious onset

• Common complaints in overhead athletes:

  • “Dead arm” sensation

  • Loss of control and strength

  • Early fatigue

• May coexist with or cause shoulder impingement

• Periscapular pain:

  • Posterior border

  • Anterior pain near the coracoid

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Physical Examination

Visual Observation

• Observe for:

  • Asymmetry

  • Winging

  • Dysrhythmia during arm elevation/lowering

• Perform Scapular Dyskinesis Test (SDT) with and without weights

Resting Position Evaluation

• Arms relaxed at sides

• Assess:

  • Vertical scapular asymmetry

  • Lateral displacement from midline

  • Scapular abduction angle (goniometer)

Dynamic Motion

• Forward flexion and lowering

• Look for:

  • Border prominence

  • Irregular or jerky motion

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Muscle Strength Testing

• Upper trapezius – shoulder shrug

• Middle trapezius – prone, arm at 90°, resist downward force

• Lower trapezius – prone, arm abducted 120°

• Rhomboids – modified Kendall test

• Serratus anterior

  • Wall push-ups

  • Look for medial border winging

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Special Tests

• Scapular Assistance Test

  • Examiner assists upward rotation/posterior tilt

  • Positive if pain decreases or motion improves

• Scapular Retraction Test

  • Scapula stabilized during impingement testing

  • Positive if pain reduces or strength improves

Additional Findings

• Local tenderness (borders, coracoid, AC joint)

• Crepitus ? possible snapping scapula syndrome

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Imaging & Diagnostic Studies

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Treatment of Scapular Dyskinesis

Non-Operative (Mainstay)

• Focused physical therapy

  • Restore flexibility first

  • Activate scapular stabilizers

• Muscle training

  • Serratus anterior

  • Lower trapezius

• Exercise progression

  • Begin below shoulder level

  • Progress to kinetic chain and sport-specific drills

Rehabilitation Timeline

• Typically 2–12 weeks

• Scapular-focused programs show better outcomes than generalized rehab

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Surgical Management

• Rarely required

• Reserved for:

  • Snapping scapula

  • Refractory scapulothoracic bursitis

  • Structural abnormalities

• Arthroscopic excision and correction

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Sport-Specific Considerations

Baseball (Throwers & Pitchers)

• High-velocity overhead throwing stresses the shoulder

• Deceleration phase causes:

  • Posterior capsular tightness

  • GIRD (Glenohumeral Internal Rotation Deficit)

• SD associated with:

  • Increased scapular internal rotation

  • Reduced shoulder rotation velocity

  • Reduced scapular motion

• Risk factors:

  • Low external rotation strength

  • Reduced internal rotation

• Rehabilitation

  • Effective when addressing posterior tightness

  • Early intervention reduces injury risk

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Swimming

• Up to 90% of propulsion from upper limbs

• Annual shoulder pain prevalence: 23–38%

• “Swimmer’s shoulder” includes:

  • Impingement

  • Rotator cuff tendinopathy

  • Instability

  • SD

• SD prevalence increases with fatigue:

  • 30% pre-training

  • 70% mid-training

  • 80% post-training

• More common in:

  • Long-distance swimmers

  • Athletes with >4 years of training

  • Male swimmers

• Conservative management leads to faster return to sport

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Tennis

• Repetitive high-velocity serving stresses the shoulder

• SD disrupts the kinetic chain

• Findings in tennis players:

  • Reduced subacromial space

  • Decreased racket velocity

• Common associated injuries:

  • GIRD

  • SLAP tears

  • Shoulder impingement

• Treatment

  • Physiotherapy focusing on:

    • Scapular control

    • Core strength

    • Posterior capsule stretching

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Key Take-Home Messages

• Scapular dyskinesis is a functional abnormality, not a standalone injury

• Strongly associated with multiple shoulder pathologies

• Athletes with shoulder pain must be assessed for SD

• Most cases respond well to scapula-based rehabilitation

• Underlying pathology should be treated alongside SD to prevent recurrence