An ACL injury is the tear or sprain of an anterior cruciate ligament – one of the major ligaments in your knee. The cruciate ligaments are found inside your knee joint and combined, the anterior and the posterior cruciate ligaments control the back and forth motion of your knee. An ACL injury is one of the most common knee injury and often occur in athletes who play physically demanding sports like soccer, football, and basketball.
According to the American Academy of Orthopaedic Surgeons, injured ligaments are considered "sprains" and are graded on a severity scale, as listed below:
- Grade 1 Sprains - The ligament is mildly damaged in a Grade 1 Sprain. It has been slightly stretched, but is able to help keep the knee joint stable.
- Grade 2 Sprains - A Grade 2 Sprain stretches the ligament to the point where it becomes loose. This is often referred to as a partial tear of the ligament.
- Grade 3 Sprains - This type of sprain is most commonly referred to as a complete tear of the ligament. The ligament has been split into two pieces, and the knee joint is unstable.