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, address loose ligaments in the front of the shoulder, and alleviate symptoms.
Initial treatment consists of medication and ice to relieve the pain, stretching and strengthening exercises, and modification of the activity that initially caused the problem. Referral to a physical therapist or athletic trainer may be recommended. Treatment is geared toward the rotator cuff and shoulder blade muscles to help stabilize the shoulder, as well as normalizing the shoulder range of motion to alleviate the contact in the back of the shoulder. An injection of cortisone to the area around the tendon (within the bursa) is rarely recommended. It is important to correct throwing mechanics and participate in an interval throwing program in order to safely return to activity. If conservative treatment fails to improve symptoms, arthroscopic surgery may be indicated to repair or debride the torn labrum and rotator cuff tissues and sometimes, to tighten a stretched anteroinferior capsule (soft tissue surrounding the joint). Return to activity is usually possible four to six months after surgery, with additional time required for return to specific sports activity such as pitching.