While repetitive strain injuries are common for athletes – whether amateur or professional –, an ACL tear is a more serious problem that can debilitate a person for months. It usually occurs as a result of a sudden stop, direct impact against another player or landing awkwardly after jumping for something high up like a ball. Rapid changes in direction can also put a lot of stress on the ACL when it's twisted or stretched too far.
This type of injury is common in contact sports such as football, soccer, basketball as well as recreational activities like skiing. Once you tear your ACL, it can be hard for the ligament to heal on its own.