What is the anterior cruciate ligament (ACL)?
When you’re trying to figure out what you may or may not have injured in your knee, it helps to understand the overall anatomy. The knee is made up of three bones: the femur (thighbone), tibia (shin), and patella (kneecap). The kneecap provides protection to the front side of the knee.
To connect these bones and form the knee, there are four primary ligaments. The cruciate ligaments are on the inside of the knee joint, with the anterior cruciate (ACL) in the front and the posterior cruciate in the back. These two ligaments form and “X” and they control the back and forth motion of the knee.
The collateral ligaments are on the sides of each knee, with the medial collateral ligament (MCL) on the inside and the lateral collateral ligament on the outside. These ligaments control the sideways motion of the knee.
The two ligaments most prone to injury are the ACL and MCL.
ANTERIOR CRUCIATE LIGAMENT (ACL)
Two ligaments in your knees are more prone to injury than others. Your ACL (anterior cruciate ligament) crosses from the back of your femur to the front of your tibia. Although it acts like a strong brace for your knee, the ACL is injured frequently because it is smaller and more susceptible to twisting.
TORN FROM A TWIST
Your ACL can be injured when you twist your knee beyond its normal range of motion. When you’re on skis, for instance, and “catch an edge”, this causes you to twist your lower leg outward or inward. In team sports, as well, with the foot planted you can twist and tear your ACL. You might hear or feel a pop, and your knee may give way. Pain and swelling results. A complete tear of the ACL is like rope fibers coming apart. A partial tear can also occur. Other parts of the knee may be injured at the same time that you injure the ACL.
MEDIAL COLLATERAL LIGAMENT (MCL)
Your MCL also connects your femur to your tibia, but this ligament runs along the inside of your joint. An outside blow to the knee or any severe impact can tear the MCL because much like a strap stretched too far, it snaps. Your knee may buckle sideways. Pain and swelling are common, and either a complex or partial tear is possible. It is not unusual to tear the meniscus or ACL at the same time.
What causes injury to the ACL?
The anterior cruciate ligament can be injured from a variety of forces. If you look at this list, you’ll understand why football and soccer players have so many ACL injuries:
• Stopping suddenly
• Rapid directional change when running
• Rapid slowing down while running
• Landing at a bad angle from a jump
• Direct contact or collision
What are the degrees of ACL injury?
About one half of ACL injuries also involve damage to surrounding structures such as the cartilage, meniscus, or other ligaments. Injured ligaments are considered “sprains” and are graded based on their severity.
• Grade 1 sprain — Ligament is mildly damaged. Slightly stretched, but can keep the knee stable.
• Grade 2 sprain — Ligament is stretched to the point it is loose. This is often called a partial tear. Partial tears of the ACL are rare.
• Grade 3 sprain — This is a complete tear of the ligament. Ligament is split and the knee is unstable. Most ACL tears are complete or near complete.
What are signs that I have injured my ACL?
In a grade 3 injury of the ACL, the person will often hear a popping sound and the knee will give out. In lesser injuries, these are symptoms of ACL damage:
• There will be pain accompanied by swelling. The injured knee will swell within the first 24 hours. The swelling and pain may resolve themselves, but if you engage in the sport or activity again, your knee will probably be unstable and you can cause further damage, particularly to the cartilage.
• Loss of full range of motion
• Tenderness along the joint line
• Pain when walking
How is an ACL injury diagnosed?
When Dr. Holmes suspects an ACL injury, physical examination will usually tell the tale. He tests range of motion, and compares the injured knee to the patient’s healthy knee. An MRI will show an ACL tear, but we can usually diagnose a tear with the physical exam alone.
Can ACL injuries be treated without surgery?
The other ligaments, such as the MCL can partially tear and can repair themselves. But partial tears to the ACL are rare, and full tears will not heal on their own. If the patient is elderly and inactive, there are non-surgical options such as bracing and strengthening the surrounding muscles. But the knee will remain weak and unstable without surgery.
How do you repair the ACL?
Patients often think that the ACL can simply be sewn back together, not unlike a broken shoelace that the person ties back together with a knot. This kind of repair of the ACL does not work, as the ligament will not fully heal and will be prone to tearing again.
To repair the ligament, a ligament graft is necessary. There are two options for these grafts. The person’s own tissue can be used, known as an autograft, or donor tissue can be used, known as an allograft. Athletes and younger patients usually prefer to use grafts from their own tissue, as they are generally stronger. The tissue is usually harvested from the hamstring tendon or the patella tendon at the beginning of the reconstruction surgery through an additional incision.
Older patients may opt to use an allograft from donor (cadaver) tissue. This provides a faster recovery and return to work for those not anticipating putting heavy stress on the ligament (as in sports).
I can not say enough wonderful things about Dr Holmes and his staff. I had been to another Orthopedic Surgeon and was completely disheartened because I felt that I would never be out of pain again. From the very first day that I stepped into Dr Holmes’ office, I was treated with respect and caring – not only by Dr Holmes, but by every member of his staff. Not only am I up and walking – but I am back at work, and my pain level is 98% less than the day that I first walked in his office door. Since my surgeries, I have recommended Dr Holmes to several people that were having orthopedic issues, and I will continue to recommend him.
How is ACL surgery done?
At Sports Occupational & Knee Surgery, Dr. Holmes performs our ACL reconstructions as outpatient surgeries. Contrary to what you may assume, these surgeries are not always immediately done after the injury. Depending on the amount until inflammation, we may wait for surgery until the swelling has decreased.
Dr. Holmes removes the torn ACL and grafts the new ligament into the femur and tibia. A more urgent reconstruction is done if a repairable meniscus tear is also suspected.
When can I return to sports after an ACL tear?
You’ve probably heard of football players coming back after tearing their ACL. When first recovering, the patient will be in a leg brace and will use crutches. This protects the knee when the person needs to get around. But we do get the patient moving the knee right away, as this aids in the eventual return of range of motion. Some patients like to use a continuous passive motion machine. This machine helps the knee keep motion and flexibility, but it doesn’t place any strain on the new ligament.
After the initial recovery, physical therapy is key for months afterward to return strength and stability to the knee, and to regain full range of motion. Most athletes can return to the sport they were injured in after about six months when using autograft tissue and about nine months when a revision ACL is performed. The return to sports depends on full return of muscle strength (usually lost due to the injury) and amount of range of motion. A knee brace is usually required for the initial return to sports.