ACL and ACL injury

Also known as: Anterior cruciate ligament injury

What is ACL injury? The anterior cruciate ligament (ACL) is a band of tough, fibrous tissue that connects the thigh bone (femur) to the shin bone (tibia). ACL provides stability for your knee. An ACL tear occurs when the ligament is stressed beyond its breaking point, causing it to rupture or stretch inside the knee. Common symptoms include:

  • A popping sound and pain in the knee
  • Swelling in the knee
  • Feeling unstable when putting weight on the leg, especially while trying to change direction
  • Noise in the knee after an injury

Injuries range from mild, such as a small tear, to severe, such as when the ligament tears completely or when the ligament and part of the bone separate from the rest of the bone.

ACL injury typically requires surgical intervention in order to return to sport. Physical therapy is recommended before surgery to restore motion in the knee and reduce or minimize swelling. Providence Sports Therapy can work with athletes to teach exercises and techniques that research shows may help prevent ACL injuries.

What are the causes?
ACL injuries are classified as contact or non-contact. A contact ACL injury may occur when an athlete gets hit in the knee, for instance, during a football tackle, and the stress on the joint is too much for the ACL to handle. Non-contact ACL injuries occur when an athlete is trying to quickly change direction or suddenly stop. The momentum through the knee may place too much force on the ACL, causing it to stretch or rupture. Poor biomechanics, strength and flexibility are contributing factors to non-contact ACL injuries.