Internal Rotation Range of Motion

Why it matters, how it’s analyzed and what the research says

Internal Rotation Range of Motion

Why it matters, how it’s analyzed and what the research says

Why it matters

Internal rotation range of motion is often asymmetrical, with less internal rotation occurring on the throwing arm. These changes are often normal adaptations of throwing, But may also be a sign of joint capsule restrictions developing in at the back of the shoulder

A loss of internal shoulder rotation is commonly called GIRD (Glenohumeral Internal Rotation Deficit) and currently defined as a loss of more than 20° of internal rotation on the throwing arm compared to the non-throwing arm.

However, the presence of GIRD is not always a bad thing and usually considered normal for a baseball player as long as the total range of motion between shoulders is symmetrical. For example, the shoulder may have 35 degrees of internal rotation and 120 degrees of external rotation on the throwing side and 55 degrees of internal rotation and 100 of external rotation on the non-throwing side. Although the athlete has GIRD, the total arc for both sides is 155 degrees.

After pitching, significant loss in internal rotation of the shoulder is seen and can become a problem if this becomes chronic over a season. These changes can alter the biomechanics of the shoulder and increase the risk of injuries like labrum and rotator cuff tears.

Analyzing Internal

Range of Motion (IR ROM)

There are two ways that we look
at internal rotation ROM:

1. Symmetry

Symmetry compares your throwing arm internal rotation range against your non-throwing shoulder. Most players have less internal rotation range in their throwing arm than their non-throwing arm.

2. Trend

Trend looks at how your range changes when compared to previous tests. Decreased range of motion by more than 10% will automatically modify your arm care and provide a recovery-based program focused on mobility.

2. Trend

Trend looks at how your range changes when compared to previous tests. Decreased range of motion by more than 10% will automatically modify your arm care and provide a recovery-based program focused on mobility.

Summary of Research
    • Players lost 9.5 degrees of internal rotation and 10.7 degrees of total motion immediately after pitching, which remained unchanged 24 hours after pitching (Reinold 2007).
    • College pitchers lost up to 17 degrees of total range of motion between the preseason to postseason (Case, 2015)
    • A study of 39 professional pitchers over a single season found that 60% of the pitchers with a GIRD of 35° during spring training experienced shoulder problems that caused them to miss playing time during the season (Amin, 2015)
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    • Pitchers with a total range of motion difference more than 5 degrees between the throwing and non-throwing arm had 2.5 times greater risk of shoulder injury (Wilk, 2002)