Symptoms of a Torn ACL

The Symptoms of a torn ACL are, unfortunately, very specific, and very reliable. If you have suffered a knee injury, and are wondering if you may have torn your ACL, read below to see if you match the symptoms of ACL knee injury.

While not every ACL knee injury presents with the same symptoms, chances are you will have several of those listed below.


Swelling is one of the most reliable symptoms of a torn ACL. ACL knee injury involves a disruption of the anterior cruciate ligament. Since this ligament is within the knee joint, swelling that occurs with a torn acl is confined within the joint. This means that your entire knee will swell, often quite a bit.

Your knee will feel very tight, and will look visibly larger than your uninjured knee. When put side by side, you will be able to tell if it is swollen. Many people describe it looking like a grapefruit - large and puffy. Your knee cap may dissappear. This type of swelling is called an effusion, as it is contained within the joint. ACL knee injuries will swell very quickly, usually within the first 10 minutes. This is important to know when you talk to your physician, because it helps to differentiate your injury from other types of knee injuries during evaluation.


Another very reliable symptom of a torn ACL, pain is very common with ACL injury. On a rare occasion I will see patients that did not have any pain with their initial injury, but this is extremely rare. Pain is usually rated as moderate to severe, 5-9 on a 10 point scale. It is usually described as sharp initially, and then may become throbbing or achey as your knee begins to swell.

Trying to straighten or bend the knee often increases pain, and this is especially true after the knee swells up.

Feeling or Hearing a "Pop"

One of the most common symptoms of a torn ACL is feeling or hearing a pop during the initial injury. Often times my patients will not be able to tell me exactly what happened when they hurt their knee, other than they felt or heard a pop, and it hurt...a lot. The pop may or not actually be the ACL tearing, or it could be from the force of the femur and tibia rubbing against each other. If you heard or felt a pop, you very well may have suffered an ACL knee injury.

Loss of Range of Motion

Because an acl knee injury causes swelling, another one of the symptoms of a torn ACL is decreased range of motion. Most commonly you will have trouble bending it, often unable to bend to 90 degrees. It may also be difficult to completely straighten it out.

Loss of Strength

Symptoms of a torn ACL also include quadriceps weakness.Again, because of the swelling and injury to the knee, the quadriceps muscles will be inhibited by the body in order to try to protect the injury. This means that you will have trouble lifting your leg, or straightening it out, both because of pain, and a feeling of weakness.

Giving Away

The anterior cruciate ligament is a major stabilizer of the knee. It helps the joint communicate with the muscles to keep the knee stable. If it is disrupted, you may have episodes where you knee feels like it gives out, or buckles. This is especially true when you walk on it, or try to turn on your injured leg. This is one of the most common symptoms of a torn ACL.


ACL knee injury is a significant sports injury. If you suffer from any of the above symptoms of a torn ACL, you should see your family physician as soon as possible. While no acl injury is exactly the same, the vast majority have some if not all of these symptoms.

Didn't find what you were looking for? Search SII for more information...

Running Pain Solutions

The key to getting rid of minor aches before they become major pains is a simple, total body prevention program.

Written for Runners by a runner, you'll learn a holistic approach to improving mobility, restoring normal movement and muscle activation patterns, and restoring the body and mind connection.

This Kindle Book contains a step by step program to keep you running pain free. Included are detailed instructions and illustrations for exercises to improve mobility, balance, neuromuscular control, strength and endurance. Only $7.49!

Get Your Copy Today!

[?] Subscribe To This Site

follow us in feedly
Add to My Yahoo!
Add to My MSN
Subscribe with Bloglines