Knee injuries are the most common injury in football. The rate of injuries during games is 8.5x greater than the rate in practices, but since players have 11x more practices than games during a season, practice injuries are a bit more common.
A football injury study was done for the 1986 and 1987 football seasons. There was a combined total of 6,229 players in the study, with 445,856 Athletic Exposures (AEs). An AE is a practice session or a game.
Of the AEs, 410,165 (92.0%) occurred in practices and 35,691 in games (8.0%). A total of 2,820 injuries were reported, for an overall injury rate of 6.32/1,000 AEs, or 45.27/100 players.
The rate in practices was 3.93/1,000 AEs; in games, 33.68/1,000 AEs. Thus the injury rate was 8.6 times higher in games than in practices (in which 57.1% of total injuries occurred). This major difference in injury rate between competition and practice is consistent with most other sports that have been studied (1-3).
Anatomic site - Total Injuries - Injuries/1,000 AEs
Knee - 522 - 1.17
Ankle - 446 - 1.00
Shoulder - 297 - 0.67
Quadriceps - 180 - 0.40
Head - 155 - 0.35
Neck - 133 - 0.30
Hamstring - 130 - 0.29
Lower back - 108 - 0.24
Finger(s) - 85 - 0.19
Pelvis, hip - 84 - 0.19
Lower leg - 81 - 0.18
Hand - 58 - 0.13
Foot - 54 - 0.12
Elbow - 53 - 0.12
Ribs - 52 - 0.12
Groin - 51 - 0.11
Toe(s) - 46 - 0.10
Thumb - 38 - 0.09
Wrist - 26 - 0.06
Clavicle - 24 - 0.05
Other - 24 - 0.05
Heel/Achilles tendon - 23 - 0.05
Forearm - 17 - 0.04
Patella - 17 - 0.04
Eye(s) - 13 - 0.03
Sternum - 13 - 0.03
Chin - 12 - 0.03
Upper back - 12 - 0.03
Nose - 11 - 0.02
Stomach - 9 - 0.02
Upper arm - 7 - 0.02
Spine - 7 - 0.02
Kidney - 5 - 0.01
Jaw - 4 - 0.01
Testicles - 4 - 0.01
Face - 3 - 0.01
Mouth - 3 - 0.01
Teeth - 3 - 0.01
Coccyx - 3 - 0.01
Scapula - 2 - 0.00
Buttocks - 2 - 0.00
Spleen - 2 - 0.00
Ear - 1 - 0.00
Totals - 2,280 - 6.32
http://www.exra.org/FB89.htm