title: The curveball as a risk factor for injury: a systematic review.
abstract: BACKGROUND
  The curveball is regarded by many as a potential risk factor for injury in youth baseball pitchers.
  
  
  OBJECTIVE
  To critically evaluate the scientific evidence regarding the curveball and its impact on pitching biomechanics and the overall risk of arm injuries in baseball pitchers.
  
  
  METHODS
  Systematic review.
  
  
  METHODS
  Level 3.
  
  
  METHODS
  Ovid MEDLINE from 1946 to 2012.
  
  
  METHODS
  Ten biomechanical studies on kinematic or electromyographic analysis of pitching a curveball were included, as well as 5 epidemiologic studies that assessed pain or injury incidence in pitchers throwing the curveball.
  
  
  METHODS
  When possible, demographic, methodology, kinetics, and kinematics variables and pain/injury incidence were compiled.
  
  
  RESULTS
  Two biomechanical studies found greater horizontal adduction of the shoulder at ball release and less shoulder internal torque during the curveball pitching motion. Two studies demonstrated less proximal force and less torque at the elbow as the arm accelerated when throwing a curveball compared with a fastball, as well as greater supination of the forearm and less wrist extension. Electromyographic data suggested increased activity of extensor and supinator muscles for curveballs. No studies found increased force or torque about the elbow or shoulder. Three epidemiologic studies showed no significant association between pitching a curveball and upper extremity pain or injury. One retrospective epidemiologic study reported a 52% increase in shoulder pain in pitchers throwing a curveball, although this may have been due to confounders.
  
  
  CONCLUSIONS
  Despite much debate in the baseball community about the curveball's safety in youth pitchers, limited biomechanical and most epidemiologic data do not indicate an increased risk of injury when compared with the fastball.
authors.affiliation: Department of Orthopaedic Surgery, Columbia University Medical Center, New York, New York.
authors.forename: W Jeffrey
authors.initials: WJ
authors.lastname: Grantham
authors.affiliation: Department of Orthopaedic Surgery, Columbia University Medical Center, New York, New York.
authors.forename: Jaicharan J
authors.initials: JJ
authors.lastname: Iyengar
authors.affiliation: Vanderbilt Bone and Joint Clinic, Franklin, Tennessee.
authors.forename: Ian R
authors.initials: IR
authors.lastname: Byram
authors.affiliation: Department of Orthopaedic Surgery, Columbia University Medical Center, New York, New York.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Ahmad
keywords: baseball; curveball; pitching; throwing injuries