ACL (anterior cruciate ligament) injuries are created when a person changes direction rapidly, the movement and the strain on the ligament causes it to snap. Since the ligament runs pretty much through your knee, your knee starts to swell and your become wobbly and unstable. This kind of injury is extremely painful. I once did a fake pass in football and injured my knee in the process. It happened when I acted like I was going to go one way and the quickly changed direction. Acl injury prevention for adults I thought I had an ACL but thankfully I had only strained a ligament in my leg. Even though I didn’t have an ACL injury, I was in excruciating pain, and couldn’t walk for a week. It is important to remember even in the heat of a game to be very careful. One wrong step could not only cost you the game but a ton of headaches later.