Evaluation of Glenohumeral Internal Rotation Deficit (GIRD)
Evaluate GIRD by measuring passive glenohumeral internal rotation (IR) bilaterally with the patient supine or sidelying, comparing the throwing/dominant shoulder to the non-throwing shoulder—a deficit ≥20° defines clinically significant GIRD.
Measurement Technique
The evaluation requires bilateral passive shoulder range of motion assessment in specific positions:
- Supine position: Measure both internal and external rotation (ER) with the shoulder at 90° abduction 1
- Sidelying position: An alternative method that provides 14° less total arc of motion but may offer more consistent stabilization. Normative values are 160° for dominant shoulder and 163° for non-dominant shoulder 2
- Key measurement: Compare IR of the throwing/dominant shoulder to the non-throwing shoulder
Diagnostic Criteria
The critical threshold is ≥20° loss of internal rotation in the dominant/throwing shoulder compared to the non-dominant side 3, 4. This represents the cutoff that indicates a shoulder at risk for injury.
Important Distinction: Anatomical vs Pure GIRD
Recent evidence distinguishes two types 5:
- Anatomical GIRD (aGIRD): Loss of IR with corresponding gain in ER, maintaining total arc of motion
- Pure GIRD (pGIRD): Loss of IR without compensatory ER gain, resulting in decreased total arc of motion—this is the pathologic form associated with injury risk
Pure GIRD is more clinically significant as it reflects true posterior capsular tightness rather than adaptive bony changes 5.
Physical Examination Components
During assessment, evaluate 1:
- Shoulder motion: Passive IR and ER at 90° abduction
- Total arc of motion: Sum of IR + ER (should be symmetric bilaterally in healthy athletes)
- Horizontal adduction: Reduced range suggests posterior capsular tightness
- Scapular positioning and motion: Assess for dyskinesis
- Rotator cuff strength: Test for weakness, particularly in external rotators and scapular stabilizers
- Pain location and timing: Specifically during late cocking and deceleration phases of throwing
Advanced Evaluation Methods
For quantitative assessment of posterior capsular tightness 3:
- Shear wave elastography: SW velocity >4.81 m/s in the throwing shoulder or a difference >0.77 m/s between shoulders indicates abnormal capsular stiffness
- MRI: Preferred imaging to assess posterior capsule thickness and concomitant soft tissue pathologies 4
- Ultrasound: Can measure posterior inferior capsule thickness, though thickness alone may not correlate as strongly as elasticity 3
Clinical Context
GIRD prevalence varies by sport: 18.1% in elite swimmers 5, with higher rates in baseball pitchers. The condition develops from repetitive overhead motion causing posterior capsular thickening and contracture 6, 7.
Common Pitfall
Do not confuse adaptive humeral retrotorsion (bony adaptation) with pathologic soft tissue GIRD. Soft tissue GIRD (ST-GIRD), which accounts for humeral retrotorsion, correlates better with function, performance, and injury risk than traditional GIRD measurements 7. Athletes may have increased ER from bony adaptation without true pathology if total arc of motion is preserved.
Red Flags During Evaluation
Look for these associated findings that suggest injury risk 1:
- Pain during throwing, particularly at ball release and deceleration
- Decreased throwing velocity or accuracy
- Focal rotator cuff weakness
- Scapular dyskinesis (abnormal scapular movement patterns)
- Reduced horizontal adduction ROM
Early detection is paramount as untreated GIRD leads to rotator cuff strength imbalances, secondary impingement, and increased risk of labral tears 4, 8.