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Can You Avoid Shoulder Injuries : The Role of the Rotator Cuff

Shoulder injuries can occur in one of two ways. Those related to recreational activity and those not related to recreational activity. Non-recreational injuries such as trauma or accidents are unpredictable and difficult to prevent. We can , however, prepare our shoulders to minimize recreational-activity related injuries.

More than 25% of all patients seeking medical help each year due to shoulder pain sustained injuries in the gym or in the sports arena. More than 20 % of all sports injuries involve the shoulder. After knee injuries , which is the most common of all sports injuries, the shoulder ranks number two among the most common injuries treated by orthopaedic surgeons.

Many sports involve movements of the arm in unnatural positions or subject the shoulder to unnatural stresses. Some activities demand performances beyond physiologic endurance limits. Elite baseball pitchers, Olympic gymnasts, whitewater kayaking, competitive water skiers, power lifters, and circus performers are all prone to shoulder injuries.

The shoulder must be responsive enough to adequately meet the demands for each specific sport event. The shoulder needs to have flexibility, strength, endurance, speed, stability , and control. Unfortunately , the shoulder, while being the most mobile joint in the body, is also the least stable joint in the body. Unlike that of the hip joint where stability is provided by a deepened bony socket that captures the hip joint, stability of the shoulder must be maintained by soft tissue structures that surround the joint. The soft tissues of the shoulder, consisting of the capsule and the labrum function as passive restraints and protect against extreme ranges of motion. These passive restraints do not contract like muscles can. The crucial soft tissue restraint are the rotator cuff muscles that surround the shoulder. The rotator cuff muscles provide dynamic stability of the shoulder contracting in a well coordinated fashion with each movement of the shoulder.

The rotator cuff muscle group is composed of four muscles that originate from the shoulder blade, one in the front, three in the back. The subscapularis muscle from the front is the largest and strongest of the four muscles and contribute up to 50% of the total rotator cuff muscle strength. The rotator cuff muscles converge to insert onto the top of the shoulder becoming the rotator cuff tendons. The key role of this group of muscles is to dynamically contract in a synergistic fashion to create a suction cup like phenomenon ( termed concavity compression) that secures the humeral head against the glenoid during movements the shoulder. The rotator cuff or cuff muscles initiate raising of the arm preparing for shoulder motion, then they stabilize the shoulder so as to allow the power muscle groups , such as the deltoid , to take over the rest of shoulder motion.

Imagine a nail driven through the shoulder joint that stabilizes the joint so as to allow movement of the shoulder via this point of secure pivot in multiple directions. This is the function of the rotator cuff. A weakened, ineffective, or torn rotator cuff tendon impairs the joint compression force resulting in looseness of the shoulder joint. This looseness, or microsubluxation, of the shoulder joint with every movement of the arm contributes to progressive damage of the labrum, leading to tears. Rotator cuff tendons eventually tear after repetitive tensile overload. Ultimately this chain of events may terminate in shoulder joint damage and leads to arthritis.

With increasing demand for shoulder activity, the more important it is to have a well-functioning rotator cuff. Even with everyday functional usage of the arm, such as raising the arm up above shoulder height, the rotator cuff encounters a force near to that individual’s body weight. With extreme sports such as power lifting, the rotator cuff may be exposed to forces up to seven times body weight.

In repetitive overhead throwing activities, particularly elite baseball pitchers, the rotator cuff is subjected to high levels of repetitive tensile stress. This action is especially strenuous the moment after the ball is released, during the deceleration phase of the throwing arm. At this moment, the external rotator muscle group has to eccentrically contract against a shoulder distracting force of up to 200 pounds in order to prevent the shoulder from being thrown out of the joint. This makes rotator cuff injury the most common injury in the throwing shoulder. Partial thickness rotator cuff tendon tears in the external rotator tendons are almost universal among throwing athletes. Repetitive micro-trauma in the posterior rotator cuff tendons caused by repetitive eccentric overload during the deceleration phase of the throwing motion eventually leads to tensile load failure resulting in tendon tears. In fact, studies have shown that among professional baseball pitchers, those with preseason weakness in the external rotators had a higher risk of in-season throwing related injury that leads to surgery than pitchers without preseason weakness. Unfortunately, less than 50% of those professional baseball pitchers who had shoulder surgery for a torn rotator cuff tendon were able to return to presurgical level of play.

So, can shoulder injuries be avoided? The answer is a definitive yes. The root cause of most recreational activity related shoulder injuries can be traced to a weakened rotator cuff. Intangible unpredictable injuries are unpreventable, but it pays to optimize and strengthen the small stabilizing muscle groups of the rotator cuff when partaking in recreational activities that involve movements of the arm.

Regular exercises to maintain the function and strength of the rotator cuff is crucial for athletes to avoid injuries to the shoulder due to repetitive tensile overload. It is like not putting on the seat belt in the car, most of the time you probably can get away with it, but you wish you had it when you need it. So it is incumbent for every athlete to strengthen the Achilles heel of the shoulder – the rotator cuff.