It is not uncommon for pitchers and overhand throwers to experience shoulder pain. This can be from multiple different causes. A common cause of pain in throwers is loss of shoulder internal rotation or GIRD (Glenohumeral Internal Rotation Deficit). This is thought to be caused from repetitive traction when throwing on the posterior capsule (ligaments in the back of the shoulder) causing the capsule in the back of the shoulder to thicken and become stiff. As the posterior capsule becomes stiff the biomechanics of the shoulder changes with loss of internal rotation.
GIRD usually presents with vague shoulder pain when throwing occurring usually in the late cocking early acceleration phase of throwing. Associated with this can be issues with shoulder blade movement (scapular dyskinesis). The combination of these two issues can cause pain and loss of performance in overhand throwers. The diagnosis of GIRD is made when there is loss of internal rotation and loss of total arc of motion in the shoulder. It is important to visualize both loss of total arc of motion and internal rotation as overhand throwers and especially pitchers have been shown to have an increase in external rotation and a compensatory decrease in internal rotation as the proximal humerus is torqued from repetitive pitching during growth. This changes the rotation of the top of the humerus which increases external rotation and decreases internal rotation as the bone remodels from this stress. This remodeling is thought to be normal and not a cause of pain. The issue with GIRD is the loss of internal rotation is greater than the gain in external rotation causing a total overall loss of motion as compared to the opposite shoulder. In a study on college level baseball players published in 2006 by Dr. Ruotolo he demonstrated that baseball players with a loss of total arc of motion and a loss of internal rotation were significantly more likely to have shoulder pain and to lose playing time because of shoulder pain.
GIRD can be treated successfully when diagnosed by simple posterior capsular stretching with the most common stretch recommended for this condition being the sleeper stretch. Also recognizing motion issues with the shoulder blade and the strengthening of the muscles around the shoulder blade can help aid in recovery of pain and performance. It is important to recognize this condition as chronic GIRD can lead to superior labral tears in overhand athletes. It is estimated that throwers are 25% more likely to suffer a labral tear if they have GIRD. Seeing an orthopedist knowledgeable in these conditions can help throwers return to pain free optimal performance.