Part IV of the shoulder series that I have going at www.zachdechant.wordpress.com.
Last week we visited external impingement in the shoulder, how it arises, and what to do. This week we'll take a look at internal impingement. Internal impingement is a pathologic condition that can lead to a whole host of problems in the shoulder. This problem is most commonly seen in overhead throwing athletes, tennis players, volleyball players, swimmers, as well as athletes involved in overhead weight lifting.
Internal impingement is the repetitive contact of the articular surface of the rotator cuff against the posterior superior surface of the glenoid and glenoid labrum. Essentially, the supraspinatus and infraspinatus become trapped between the humeral head and the rim of the glenoid in the back of the shoulder. This happens when the arm is abducted and externally rotated or the "high 5" position as I like to refer to it. When we look at sporting activities this encompasses it's the exact position for throwing, or serving in tennis.
Contact between these structures happens naturally but not everyone presents symptomatic with pain. When internal impingement is ignored rotator cuff and labral fraying can occur which can lead to full on cuff tears SLAP tears, and labral lesions; not a good thing for the shoulder.
The precise cause of these impingement lesions remains unclear. However, it is believed that varying degrees of glenohumeral instability, posterior capsular contracture, and scapular dyskinesis may play a role in the development of symptomatic internal impingement.
Overhead athletes are pre-disposed to internal impingement purely because of the physiologic adaptations that they develop which include humeral retroversion, anterior laxity, increased external rotation, etc. The same characteristics that allow an individual to throw hard also cause dysfunction in the shoulder.
When pitchers lay back into maximal external rotation the head of the humerus is allowed to slide anteriorly in the gleniod. With the inability to stabilize the humerus dynamically at high speeds the posterior cuff gets pinched between the gleniod and the humerus. Athletes usually complain of pain on the posterio-superior region of the shoulder when the arm is externally rotated into the throwing position.
Exact causes of internal impingement aren't exactly clear but there are several theories on what causes internal impingement but most start with anterior laxity, the inability of the rotator cuff to stabilize dynamically, scapular dysfunction, as well as posterior tightness.
The first place to start in the rehabilitation of internal impingement symptoms is to restore total motion to the glenohumeral joint, namely the posterior musculature. This can be done by stretching with the sleeper stretch as well as cross body adduction.
From there we also want to emphasize strengthening the rotator cuff statically, then dynamically. Anything to strengthen the cuff and major players in the role of proper scapular function is warranted, especially upward rotation.
The one thing we don't want to emphasize is any external rotation stretching. The anterior capsule is already loose enough due to the nature of their skill. When we stretch we are concerned with increasing movement through internal rotation.
The main take home points for internal impingement are to restore motion, especially internal rotation, strengthen the cuff and scapular stabilizers, and look to restore proper motion in the scaps.