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Throwing injuries: Biomechanics and mechanism of injury

Craig Young, MD
Section Editors
Karl B Fields, MD
Joseph Chorley, MD
Deputy Editor
Jonathan Grayzel, MD, FAAEM


Millions of people throughout the world participate in sports that involve throwing or throwing-like movements. These movements range from classic ball throwing, as performed by baseball pitchers or cricket bowlers, to throwing implements other than balls, such as a javelin, to throwing-like actions that do not involve a ball directly, such as a tennis serve. All such movements involve complex biomechanics and great stresses being placed on the musculoskeletal system. Improper biomechanics, excessive stress beyond the capacity of an individual’s musculoskeletal system, or cumulative trauma from throwing too frequently can cause injury.

This topic will review the biomechanics of throwing and the relationship of these biomechanics to common throwing-related injuries. The clinical presentation and diagnosis of specific injuries are discussed separately. (See "Throwing injuries of the upper extremity: Clinical presentation and diagnostic approach".)


While the prototypical throwing athlete in the United States is a baseball player, many athletes use similar motions, including softball players, American football quarterbacks, javelin throwers, cricket bowlers, and water polo players. In addition, athletes involved in sports with repetitive overhead motions such as swimming, tennis, and volleyball often suffer similar injuries.

Based on 2009 census data, it is estimated that there are approximately 11.8 million softball players, 11.5 million baseball players, 10.8 million tennis players, 10.7 volleyball players, and over 50 million swimmers in the United States alone. At the high-school level, 2012 data from the United States National Federation of High School Sports report that there are over 475,000 baseball players, 380,000 softball players, 340,000 tennis players, and 90,000 tennis players, and almost 19,000 water polo players.

Upper extremity injuries are common in the overhead athlete and account for 75 percent of the time missed from sport among collegiate baseball players [1]. A cohort study with 10-year follow-up of 481 youth pitchers revealed that 5 percent experienced serious injury (defined as injury requiring elbow or shoulder surgery or retirement from pitching) over that time [2]. Most of these upper extremity injuries are caused by overuse. Risk factors among baseball players include position (pitchers and catchers are at greatest risk), high number of pitches per game (ie, high pitch counts), high number of innings pitched, higher pitch velocity (pitchers who throw harder are at greater risk of injury), year-round play, and inadequate recovery time between throwing sessions (games or practice) [1-8]. Year-round play in particular is thought to the increase the injury rate among youth baseball pitchers [5,6,9].


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Literature review current through: Sep 2016. | This topic last updated: May 11, 2015.
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