Overhead Athlete Injuries: What Is Internal Impingement?

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By Kyle Temme, PT, DPT

“Internal Impingement” is an overuse injury seen in overhead athletes, caused by the repeated pinching of the rotator cuff between the humerus (ball) and glenoid (socket) during the throwing motion.

3 Signs of Internal Impingement

(Corpus 2016)

1. Tenderness on the back of the shoulder joint (posterior glenohumeral joint line)

2. Increased shoulder external rotation

3. Decreased shoulder internal rotation

A dpt looks for signs of injury in the rotator cuff area of a man's arm

Causes of Shoulder Internal Impingement

Internal impingement is multifactorial, and most often arises due to a combination of:

1. Physiologic remodeling of the shoulder

a. Increased retroversion of the humeral head and glenoid. An adaptation commonly seen in overhead athletes is that the humerus actually begins to twist over time to accommodate the throwing motion. This is one reason why throwers often have excessive external rotation on their throwing side.

b. Increased anterior capsular laxity. As the back side of the shoulder starts to tighten up (as we’ll discuss next), the front side does the opposite, becoming more mobile.

2. Posterior capsule contracture (tightening of the back side of the shoulder joint). This leads to a loss of the shoulder’s ability to internally rotate.

a. A loss of 15 degrees or more of internal rotation in the throwing shoulder is a risk factor for injury.

b. A loss of > 25 degrees increases the risk for the development of labrum tears (specifically SLAP lesions) as a result of increased “posterosuperior peel back on the labrum” (Burkhart 2003).

c. Throwers with ulnar collateral ligament insufficiency at the elbow demonstrate a greater loss of internal rotation compared to throwers without a history of elbow injury (Dines 2009), suggesting a correlation between these deficits at the shoulder and elbow.

3. Scapular dyskinesis

a. When the scapula is unable to effectively transmit energy from the trunk to the throwing arm or stabilize the shoulder properly:

i. Throwing mechanics become inefficient and throwing velocity can suffer.

ii. Throwers will then compensate by recruiting other surrounding musculature and increasing stress across the shoulder joint.

Treatment

Physical therapy for shoulder internal impingement has shown to be effective in reducing pain and risk of injury in multiple studies and is therefore the recommended first-line treatment.

The primary focus of therapy for internal impingement should be correction of the risk factors listed previously.

1. Shoulder range of motion deficits

a. Sleeper stretch to restore shoulder internal rotation