![]() ![]() Scapular Rotation Dysfunction (SICK Scapula) This loss of internal rotation puts throwers at greater risk for labral and rotator cuff tears. A natural and common result is that the soft tissues in the back of the shoulder tighten, leading to loss of internal rotation. Glenohumeral Internal Rotation Deficit (GIRD)Īs mentioned above, the extreme external rotation required to throw at high speeds typically causes the ligaments at the front of the shoulder to stretch and loosen. Occasionally, the thrower may feel the arm "go dead." A common term for instability many years ago was dead arm syndrome. Pain and loss of throwing velocity will be the initial symptoms, rather than a sensation of the shoulder slipping out of place. If the rotator cuff structures are not able to control the laxity, then the shoulder will slip slightly off-center (subluxation) during the throwing motion. In throwers, instability develops gradually over years from repetitive throwing that stretches the ligaments and creates increased laxity (looseness). When the shoulder is loose and moves out of place repeatedly, it is called chronic shoulder instability. Shoulder instability occurs when the head of the humerus slips out of the shoulder socket (dislocation). Internal impingement may be due to some looseness in the structures at the front of the joint, as well as tightness in the back of the shoulder. Internal impingement may also damage the labrum, causing part of it to peel off from the glenoid. This is called internal impingement and may result in a partial tearing of the rotator cuff tendon. Internal Impingementĭuring the cocking phase of an overhand throw, the rotator cuff tendons at the back of the shoulder can get pinched between the humeral head and the glenoid. When the rotator cuff tendons are injured or damaged, this bursa can also become inflamed and painful. The bursa allows the rotator cuff tendons to glide freely when you move your arm. There is a lubricating sac called a bursa between the rotator cuff and the bone on top of your shoulder (acromion). Problems with the rotator cuff often lead to shoulder bursitis. In some cases, the tendon can tear away from where it attaches to the humerus. Rotator cuff tendon tears in throwers most often occur within the tendon. The rotator cuff and labrum are the shoulder structures most vulnerable to throwing injuries. As a result, the throwing athlete can sustain a wide range of shoulder injuries. ![]() When one structure - such as the ligament system - becomes weakened due to repetitive stresses, other structures must handle the overload. Once the ball is released, follow-through begins and the ligaments and rotator cuff tendons at the back of the shoulder must absorb significant stresses to decelerate the arm and control the humeral head. ![]() During acceleration, the arm rapidly rotates internally. Over time, the ligaments loosen, resulting in greater external rotation and greater pitching speed, but less shoulder stability. This arm position of extreme external rotation helps the thrower put speed on the ball however, it also forces the head of the humerus forward, which places significant stress on the ligaments in the front of the shoulder. In order to generate maximum pitch speed, the thrower must bring the arm and hand up and behind the body. Of the five phases that make up the pitching motion, the late cocking and follow-through phases place the greatest forces on the shoulder. American Academy of Orthopaedic Surgeons, 1990, pp 293-302. Reproduced and adapted with permission from Poss R (ed): Orthopaedic Knowledge Update 3. ![]()
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