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With nearly 200,000 little league teams in this country and baseball season upon us, a local baseball coach recently asked me about injuries among young pitches and what happens inside the shoulder and elbow during pitching.

The baseball pitch can be divided into five main stages. During stage 1, called the windup, the elbow is flexed, the shoulder is in slight internal rotation and muscular activity is low. In stage 2 (or early cocking), the ball leaves the nondominant gloved hand and ends when the forward foot contacts the ground. The shoulder begins to abduct and externally rotate, activating the deltoid and rotator cuff musculature. In stage 3 (late cocking), further shoulder abduction and maximal external rotation take place. During this phase, contraction of the rotator cuff muscles reaches its peak and muscles around the scapula are activated, generating tremendous shear force across the front of the shoulder. In the 4th stage (acceleration), the shoulder muscles create a large forward force on the arm. This results in internal rotation and adduction of the humerus as well as rapid elbow extension. This stage ends with the baseball being release with huge valgus stresses along the medial side or inside of the elbow. This is the phase where most elbow injuries take place. In the 5th and final stage (follow through), all excess energy is dissipated as the arm decelerates rapidly. The elbow comes into full extension during this phase and the shoulder is maximally internally rotated. The shoulder muscles contract to try and keep the humeral head or ball in the socket.

There is a growing number of injuries seen in young athletes, particularly with some young athletes throwing year round.  Most of the injuries that occur in throwing athletes involve the shoulder and elbow joints. Moreover, the repetitive stresses placed on joints by pitching can actually alter the developmental anatomy of the shoulder and elbow over time in adolescent throwing athletes. With years of repetitive throwing in players who are still developing there can be a gradual increase in the amount the shoulder rotates outward with an associated loss of shoulder internal rotation. Coaches and parents should look for loss of shoulder internal rotation in young throwing athletes. If discovered, these athletes should do therapy exercises to correct this.

The most common shoulder injury seen in young throwers is to the growth plate at the top of the humerus. These athletes present with diffuse shoulder pain that becomes worse with throwing. There may have been an increase in throwing frequency prior to the onset of symptoms. Treatment includes 2-3 months of no throwing followed by a progressive throwing program with attention to throwing mechanics and an emphasis on control not speed.

Injuries to the elbow actually occur more frequently than shoulder injuries in adolescent baseball players. These injuries normally occur as a result of repetitive stresses.  There is tension overload of the medial structures of the elbow creating inflammation of the growth plate on the inside of the elbow. Young throwers usually experience elbow pain on the inside of their elbow and report a decrease in throwing effectiveness as well as throwing distance. Young throwers can also experience compression injuries on the outside of the elbow. Patients report dull pain, swelling, and possible locking and catching in the elbow joint. Again, treatment for these young athletes usually consists of rest from throwing until they are symptom free and then a gradual return to throwing.

Coaches should limit the number of pitches these young athletes throw in order to decrease the stresses of throwing. The USA Baseball Medical and Safety Advisory Committee have a simple table that can be followed outlining the number of pitches a young pitcher should throw.  Furthermore, young pitchers should avoid throwing sliders or curveballs until they are finished growing and should also avoid year round baseball. Young pitchers should have a minimum of 2-3 months of complete rest from throwing per year. It is a common misperception among coaches and parents that pain in the shoulder or elbow is a result of weak muscles that need to be strengthened. Instead, joint pain while throwing should be regarded as a potential injury.