A multivariate risk analysis of selected playing surfaces in the National Football League: 1980 to 1989. An epidemiologic study of knee injuries.

This study focuses on the injury rates for natural grass and AstroTurf surfaces and the risk factors of game position and type of play. We examined the game-related knee sprains, medial collateral ligament sprains, and anterior cruciate ligament sprains that occurred in the National Football League during the 1980 to 1989 seasons. The findings are controlled for categories of severity (number of games missed due to injury), position, and situation (rushing or passing) at the time of injury. The analysis of the data incorporates epidemiologic techniques associated with incidence density ratios. The data show that there is a statistically significant difference between the higher AstroTurf injury rates for knee sprains. When knee sprains are separated into medial collateral ligament sprains and anterior cruciate ligament sprains, only the anterior cruciate ligament sprains show a statistically significant higher injury rate for AstroTurf. When simultaneous control variables are considered, significantly more knee sprains occurred to backs on rushing plays and linemen on passing plays. When controlling the data for severity, only the Category II injuries (three or more games missed) sustained by linemen on passing plays had statistically significant higher injury rates for the AstroTurf. For medial collateral ligament sprains, only the Category II injuries for linemen on passing plays remain statistically significant. The data for the ACL sprains show statistically significant differences between the injury rate on natural grass and the injury rate on Astro Turf under conditions of special teams play.