Bruises, sprains, . Bruises, sprains, torn cartilage. The most common ligament injury is a sprained medial collateral ligament (mcl) which usually is treated without surgery. The most common surgical knee injury in football is a torn anterior cruciate ligament (acl). Meniscal (cartilage) tears are also common, often requiring surgery.
ACL tears. ACL tears are very common, so are meniscus tears. If you incur one of these, usually surgery is required.
Many. The primary injuries would be a anterior cruciate ligament tear, medial or lateral collateral ligament strain or tear and quite often meniscal injuries to name a few.
Preseason condition. I love football! Unfortunately there are no exercises, braces, dietary supplements that can prevent injury in this game. Without a doubt the better condition you are in at the beginning and throughout the season will be helpful to get out of your stance, run, cut, make your play while hopefully avoiding injury. Aerobics, strength and flexibility are all important in injury prevention.