The anterior cruciate ligament (ACL) is one of the four major ligaments of the knee. This ligament prevents excessive motion of the knee joint and it's located deep inside the knee. This ligament can be injured in any activity, but sports such as soccer, football, and basketball have a higher rate of injury. If you injure this ligament, you may require physical therapy or surgery to return to full activity.
This ligament can be injured in several ways, primarily we say contact or non-contact injuries. This means that you can injure the ACL by having direct contact to the knee or if you change direction rapidly, stop suddenly, or land from a jump incorrectly.
Males and females are both subject to this injury, although several studies have shown that female athletes have a higher incidence of ACL injury than male athletes in certain sports. There are many proposed reasons for this, but it has also been shown that a comprehensive conditioning program aimed at preventing ACL injuries is very beneficial.
Three bones meet to form your knee joint: your thighbone (femur), shinbone (tibia), and kneecap (patella). Your kneecap sits in front of the joint to provide some protection.
Bones are connected to other bones by ligaments. There are four primary ligaments in your knee. They act like strong ropes to hold the bones together and keep your knee stable.
These are found inside your knee joint. They cross each other to form an "X" with the anterior cruciate ligament in front and the posterior cruciate ligament in back. They control the back and forth motion of your knee.
The anterior cruciate ligament runs diagonally in the middle of the knee. It prevents the tibia from sliding forward, as well as provides rotational stability to the knee.
Injures to the ACL can occur to just this ligament, but about half of all injuries to the anterior cruciate ligament occur along with damage to other structures in the knee, such as articular cartilage, meniscus, or other ligaments.
Injured ligaments are considered "sprains" and are graded on a severity scale.
Grade 1 - The ligament is mildly damaged. It has been slightly stretched, but is still able to help keep the knee joint stable.
Grade 2 – The ligament stretches to the point where it becomes loose. This is often referred to as a partial tear of the ligament.
Grade 3 - The ligament has been split into two pieces, and the knee joint is unstable. This is most commonly referred to as a “tear”. Most ACL injuries are complete or near complete tears.
When you injure your ACL, you may feel your knee give out or hear a "popping" noise. It may not hurt at first, but most people have difficulty walking whether it hurts or not.
Other possible symptoms include:
During your first visit, be prepared to explain how you hurt your knee and how it feels since the injury. The more you can explain to your provider, the more they can understand your symptoms and medical history.
At your visit, your provider will perform a physical exam and evaluate all the structures of your knee. You will receive an x ray to determine if there are any fractures present. X ray can not detect ligament injuries but can rule out bone problems.
Most ligament injuries can be diagnosed with a thorough physical examination of the knee, but other tests, such as a Magnetic Resonance Imaging (MRI) scan may be ordered.
The MRI creates better images of soft tissues like the anterior cruciate ligament. However, an MRI is usually not required to make the diagnosis of a torn ACL, but can assist in evaluating additional structures in the knee, such as the meniscus.
Treatment for an ACL tear comes down to two options:
An athlete involved in sports will most likely require surgery to safely return to the same level of activity. The less active, usually older, individual may be able to return to a quieter lifestyle without surgery.
A torn ACL will not heal without surgery. Nonsurgical care may be effective for you if you have a lower activity level. If the overall stability of the knee is intact, this option may be your best route to care for the ACL injury. You may be recommended a brace to protect your knee from instability. A well-developed physical therapy program that involves specific exercises to restore function to your knee and strengthen the leg muscles that support it will be recommended.
Most ACL tears cannot be stitched back together. Physicians need to surgically repair the ACL to restore knee stability. This procedure requires your injured ligament being replaced with a tissue graft. This graft acts as the new ACL and can be as strong or stronger than your original ligament.
There are many types of grafts. Here are a few:
There are advantages and disadvantages to all graft sources. You should discuss graft choices with your orthopedic surgeon to help determine which is best for you.
It may take six months or more before you can return to all activities after surgery.
Whether your treatment involves surgery or not, rehabilitation plays a vital role in getting you back to your desired level of activities. A physical therapy program will guide you in regaining knee strength and function.