Living your best life with arthritis.

What is an ACL injury?

Knee anatomy

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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.

close up of arms on kneesThere is an increased chance of arthritis in patients who tear their ACL, regardless of whether or not they have surgical treatment for their injury. Research shows that anywhere from 10% to 90% of people show some level of post-traumatic arthritis after they have incurred an ACL injury. In a study by Barenius et al American Journal of Sports Medicine 2014, researchers showed that ACL reconstructed knees had a 3 times greater incidence of post-traumatic arthritis regardless of graft type using a grade of 2 or greater on the Kellgren-Lawrence.

It is important to note that an ACL reconstruction will not prevent arthritis – the purpose of the surgery is to help regain stability of the knee and to prevent further injury to the meniscus and articular cartilage due to the knees giving way.

Researchers have categorized the potential causes of post-traumatic arthritis into two groups: time of the injury and post-surgical. The first category can include “bone bruise”, inflammation, and meniscal injury. Bone bruise is indicated on most MRI and results in damage to the articular cartilage and underlying subchondral bone. Researchers believe that this damage progresses overtime, leading to post-traumatic arthritis. Inflammation from the initial injury can cause abnormal tissue remodelling and damage. Meniscal injury can be a predictor of future arthritic changes.

Altered knee kinematics, inflammation, and inadequate rehabilitation are all potential post-surgical factors. Having a reconstructed knee can alter your gait and lead to abnormal shift of contact pressures, contributing to post-traumatic arthritis. Post-surgical inflammation can negatively affect the knee cartilage and further alter knee kinematics. Proper rehabilitation is needed to regain full range of motion and strength as well as normalization of gait and movement patterns.

Athletes play an important role in preventing post-traumatic arthritis. Preventative measures include education, doing proper stretch exercises, using proper technique, and wearing the proper safety equipment. Reactive measures include rehabilitation, physiotherapy, and regular monitoring and doctor visits.