Injuries to Young Baseball Pitchers

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.

  1. During stage 1, called the windup, the elbow is flexed, the shoulder is in slight internal rotation and muscular activity is low.

  2. In stage 2 (or early cocking), the ball leaves the nondominant gloved hand and ends when the forward foot contacts the ground.

  3. The shoulder begins to abduct and externally rotate, activating the deltoid and rotator cuff musculature.

  4. 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.

  5. 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.

  6. 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 inc