Glenohumeral Internal Rotation Deficit (GIRD)
GIRD refers to a \(\leq 20^\circ\) loss of GHJ IR in the throwing shoulder compared with the nonthrowing shoulder1
GIRD refers to a loss of \(\leq 20^\circ\) IR between the throwing shoulder and the non-throwing shoulder2. Normally the difference should be within 18–20 degrees.
Pathophysiology
Shortening of the posterior capsule causes a loss of shoulder IR, which predisposes baseball pitchers to a higher potential for shoulder injury2.
Etiology
“This repetitive overhead motion in skeletally immature athletes leads to osseous adaptations initially, but with skeletal maturity, the torque and force experienced through the shoulder leads to changes in range of motion, specifically increased external rotation and decreased internal rotation, which could lead to glenohumeral internal rotation deficit.”1
Significance
Wilk et al. demonstrated that pitchers with GIRD are almost twice as likely to be injured than those without GIRD1
Calculation
| Item | j |
|---|---|
| GHJ IR Deficit (GIRD) | Difference in IR between shoulders |
| GHJ ER Gain (GERG) | Difference in ER between shoulders |
\[ \textrm{GIRD} = (\textrm{IR ROM Throwing shoulder}) - (\textrm{IR ROM C/L shoulder}) \]
\[ \textrm{GERG} = (\textrm{ER ROM Throwing shoulder}) - (\textrm{ER ROM C/L shoulder}) \]
\(\frac{\textrm{GIRD}}{\textrm{GERG}} > 1\) is associated with high risk of shoulder injury2.