When you're chasing the soccer ball down the field, your mind is on little else. That is, until you try to turn around only to hear a pop and feel your knee give out. And while it may be tempting to keep playing, these are classic signs of a torn ACL—a serious, but common, injury.

What is the ACL?

In your knee, there are four bones—the fibula, the tibia, the femur, and the patella (kneecap). These bones are held together by ligaments. Your femur and tibia are held together by a ligament called the anterior cruciate ligament, or ACL. The ACL's main job is to keep the tibia from moving too far forwards.

What are the symptoms of a torn ACL?

The moment you tear your ACL, you may hear a loud popping noise followed by your knee buckling or giving out. Almost immediately after injuring your ACL, your knee will start to swell as cartilage fluid and blood pool around the area. The pain from the swelling can be severe, and your doctor may drain the excess blood and fluid to provide you with some relief.

In addition to pain, your knee will feel unstable. You may feel like your knee will give out if you put too much weight on the knee or change directions too quickly. However, you may also find you can run without pain, so long as you're going in a straight line.

How is it diagnosed?

To diagnose a torn ACL, your doctor will examine the knee. Your doctor may perform a Lachman Test, where they pull the shin forward while keeping the thigh stable. As the ACL connects the thigh bone (femur) to the shin bone (tibia), the Lachman Test allows your doctor to feel how stable this connection is. If the shin bone is moving excessively, that indicates a torn ACL.

In order to see if any other surrounding structures are also injured, your doctor may order x-rays or an MRI.

What can cause a torn ACL?

A torn ACL is usually caused by changing directions very quickly, or by being tackled. This injury is common amongst athletes that play high contact sports such as soccer and football.

How is it treated?

In some instances, a torn ACL can be treated with a knee brace, rest, and physical therapy. This treatment is used mainly in older patients that live fairly calm, sedentary lifestyles, or in children that are not yet full grown—meaning their growth plates are still open, and the knee may repair itself.

Surgery is often necessary for patients that lead more active lifestyles, or those that want to return to a sport. A torn ACL is repaired by taking a graft from a nearby tendon—common tendons used include the hamstring tendon and the quadriceps tendon. The graft joins together the torn pieces of the ACL. Recovery time will depend on how severe the injury was, as well as your age. Physical therapy may be able to speed up the length of your recovery.

Continuing to play soccer on a torn ACL will only lead to more damage. If you suspect you may have a torn ACL, it's important to rest the injury and head to your doctor or a clinic such as The Orthopaedic Center.