Background Ankle sprains have one of the highest recurrence rates among all lower extremity injuries in sports.

Objective Assess the association between ankle sprain history in the past year and incident ankle sprain in games.

Design Retrospective Cohort Study

Setting U.S. National Basketball Association (NBA)

Participants All players who participated in an NBA game over 2 or more seasons from 2013–14 through 2016–17.

Assessment of Risk Factors History of ankle sprain in the past year was defined in a time-dynamic manner as any bilateral ankle sprain (game or non-game) in the 365 days prior to the game of interest. Hazard ratios (HR) and 95% confidence intervals (CI) were calculated while controlling for years in the NBA, body mass index, and average NBA minutes played in the prior year.

Main Outcome Measurements All acute-onset ankle sprains reported in games were identified from the NBA standardized electronic medical record (n=30 teams).

Results Across this 4-season study, 482 incident ankle sprains were reported in NBA games among 681 players and 2,517,549 player-minutes. Of the players that sustained an incident sprain, 44% (n=211) had at least one ankle sprain in the prior year. Compared to players with no sprains in the past year, the risk of incident ankle sprain increased with increasing number of prior ankle sprains; a 28% increase in risk (adjHR=1.28, 95% CI 1.03, 1.58) with one prior sprain, a 51% increase in risk (adjHR=1.51, 95% CI 1.10, 2.04) with two prior sprains, and a 100% increase in risk (adjHR=2.00, 95% CI 1.31, 2.94) with three or more prior sprains.

Conclusions History of ankle sprain in the past year was associated with increased risk of incident ankle sprain among NBA players. 44% of players had at least one ankle sprain (game or non-game) within one year prior to the incident sprain.