|POSTERIOR OR INTERNAL IMPINGEMENT
This impingement occurs in the abducted and externally rotated arm. The under surface of the posterior superior rotator cuff is pinched between the labrum and the greater tuberosity. It is most commonly seen in racket sport players and in people who sleep with their arms above their heads.
(figure of internal impingement)
Posterior Capsule Tightness
If this is tight, as is often the case when internal impingement occurs, the glenohumeral contact point will shift posteriorly and superiorly. The humerus will adopt a position of slight retroversion, stretching the anterior joint capsule leading to increased risk of anterior subluxation.