Epidemiology of Major League Baseball injuries.

BACKGROUND: Little is known about the injury rates in Major League Baseball (MLB) players, as a formal injury surveillance system does not exist. The goal of this study was to characterize the epidemiology of MLB injuries over a 7-year period.

HYPOTHESIS: Injuries in MLB would be common.

STUDY DESIGN: Descriptive epidemiologic study.

METHODS: The authors analyzed the MLB disabled list data from 2002 through 2008. Injuries were analyzed for differences between seasons, as well as during seasons on a monthly basis. The injuries were categorized by major anatomic zones and then further stratified based on injury type. Position-specific subanalyses for pitcher and position players were performed.

RESULTS: From the 2002 season through the 2008 season, an average of 438.9 players per year were placed on the disabled list, for a rate of 3.61 per 1000 athlete-exposures. There was a significant 37% increase in injuries between 2005 and 2008. The highest injury rate during the season was during the month of April (5.73/1000 exposures) and the lowest in September (0.54/1000 exposures). No differences were noted in the injury rates between the National League and the American League (incidence rate ratio [IRR] = 1.06; 95% confidence interval [CI] = 0.98, 1.15). Pitchers experienced 34% higher incidence rates for injury compared with fielders during the study period (IRR = 1.34; 95% CI = 1.25, 1.44). Among all player injuries, upper extremity injuries accounted for 51.4% while lower extremity injuries accounted for 30.6%. Injuries to the spine and core musculature accounted for 11.7% while other injuries and illnesses were 6.3% of the total disabled list entries. There was a significant association between position played and anatomic region injured (P < .001), with pitchers experiencing a significantly greater proportion of injuries to the upper extremity (67.0%; 95% CI = 63.1%, 70.9%) compared with fielders (32.1%; 95% CI = 29.1%, 35.1%). Conversely, fielders experienced a significantly greater proportion of injuries to the lower extremity (47.5%; 95% CI = 43.8%, 51.1%) compared with pitchers (16.9%; 95% CI = 14.9%, 18.8%). The mean number of days on the disabled list was 56.6. Overall, a greater proportion of disability days were experienced by pitchers (62.4%; 95% CI = 62.0%, 62.8%; P < .001) compared with fielders (37.6%; 95% CI = 37.3%, 37.9%).

CONCLUSION: Injuries in MLB resulting in disabled list designation are common. Upper extremity injuries were predominant in pitchers, while lower extremity injuries are more common in position players. These data may be used in the development of a formal MLB injury database, as well as in the development and implementation of specific preseason training and in-season conditioning for injury prevention.