This communication focuses on lesions of the throwing arm in adolescents which occur during participation in organized youth baseball. While it is apparent that multiple injuries may be possible in this sport, this communication centers on those lesions unique to the act of throwing—those lesions which occur as a direct result of prolonged and repetitious delivery of a baseball.
Insight into these lesions may be gained by an understanding of the basic act of pitching. This is best demonstrated in the professional pitcher.
The Pitching Act
The professional pitcher in the act of pitching demonstrates several distinct phases. First, there is the windup; then the arm is cocked; the arm and shoulder are accelerated and the ball is released; and finally, there is the follow-through (Fig 1).
The Cocking Phase.—
To further clarify the process, we arbitrarily divided the pitching act into three phases. In the initial phase, the arm
Tullos HS, King JW. Lesions of the Pitching Arm in Adolescents. JAMA. 1972;220(2):264–271. doi:10.1001/jama.1972.03200020072016