Internal Impingement

Internal impingement, or posterior-superior glenoid impingement, describes painful contact between the greater tuberosity of the humerus (arm bone) and the posterosuperior glenoid (socket). When the arm is cocked backwards to throw, the humerus rotates until there is contact between the labrum on the glenoid and the undersurface of the rotator cuff muscles on the humeral head. This repetitive contact results in a tearing of the labral and rotator cuff tissues. In addition, repetitive throwing can cause the anterior (front) ligamentous stabilizers of the shoulder to also stretch out and allow the humerus to shift forward, thus increasing the severity of the internal impingement

Painful internal impingement without tears of the labrum or rotator cuff may improve with conservative treatment consisting of avoidance of aggravating activities, rehabilitation exercises, correction of throwing mechanics and gradual return to overhead activities. Internal impingement with labral and/or rotator cuff tears often require arthroscopic surgery to repair tears and address loose ligaments in the front of the shoulder to alleviate symptoms.