According to a study of high school basketball players by the National Athletic Trainers' Association [1] (NATA):
Twenty-two percent of all male basketball players sustained at least one time-loss injury each year.
Approximately 42% of the injuries were to the ankle/foot, far outnumbering other injured body categories such as hip/thigh (11%) and knee (9%).
Sprains [2] were the most common type of injury (43%).
General trauma was the second most common type of injury (22%).
Sixty percent of the injuries occurred during practice.
Fifty-nine percent of game-related injuries occurred during the second half of the game.
Links:
[1] http://www.nata.org/
[2] http://www.momsteam.com/alpha/features/health_safety/ankle_sprains.shtml