Reconstruction of the anterior cruciate ligament (ACL) is a surgery designed to restore knee stability and strength after the ligament has been torn. The remnants of the torn ligament must be removed and replaced with another ligament from your body or with tissue from a cadaver.

The knee is a hinge joint where the femur, or thighbone, meets the tibia, or shinbone. This important joint is held together by these four ligaments, which connect bones to one another:

  • anterior cruciate ligament (ACL)
  • medial collateral ligament (MCL)
  • lateral collateral ligament (LCL)
  • posterior cruciate ligament (PCL)

Your ACL runs diagonally between the femur and the tibia and keeps the tibia from slipping in front of the femur. It also provides stability to the knee when it rotates from side to side.

An ACL tear is one of the most common knee injuries, especially among people who participate in high-impact sports like:

  • basketball
  • football
  • soccer
  • skiing
  • hockey

The majority of those injuries occur without impact to another player, according to the American Academy of Orthopaedic Surgeons (AAOS). They most often occur when an athlete twists or pivots during play.

There are about 200,000 ACL injuries every year in the United States, and according to the AAOS, about half of those injured undergo ACL reconstructive surgery.

ACL reconstructive surgery is done to repair a torn ACL and regain stability and movement in the knee. While not all cases of a torn ligament require surgery, very active people or those in persistent pain may opt for surgery.

ACL reconstruction is often recommended if:

  • you are young and active
  • you suffer from persistent knee pain
  • your injury causes your knee to buckle during routine activities, such as walking
  • you are an athlete who wants to remain active

You will have appointments with your doctor and surgeon prior to surgery. You’ll discuss treatment options, undergo several knee examinations, and make a decision about which type of anesthesia to use during surgery. During these meetings, it’s important to ask questions.

Discuss with your doctor where the surgically-implanted tendon will come from. Typical sources for these tendons include:

  • patellar tendon: the tendon that attaches the bottom of your kneecap, or patella, to your tibia
  • hamstring: the tendon that connects the long muscles in the back of your leg to the back of your knee
  • quadriceps: a tendon from the front of the thigh. This type of graft is typically reserved for taller or heavier patients, or for people who have had previous unsuccessful grafts.
  • cadaver: tissue from a dead body, which is called an allograft

While all cadavers are carefully screened for disease prior to surgery, some people have concerns about using dead tissue. Discuss any concerns you have with your doctor.

Your doctor will give you complete instructions for the day of your surgery. Instructions may include fasting for 12 hours prior to surgery and refraining from taking aspirin or blood-thinning medications.

Make sure to arrange to have someone come with you for surgery. It’s helpful to have another person listen to post-operative instructions and to drive you home.

You’ll be prepped for the surgery by changing into a hospital gown and having an intravenous (IV) line placed in your arm. The IV will allow the surgical team to administer medications, anesthesia, or sedatives.

Once the sample tissue is selected, it’s either surgically removed from your body or prepared from a cadaver. The tendon is then outfitted with “bone plugs,” or anchor points, to graft the tendon into the knee.

During surgery, a small incision is made in the front of the knee for an arthroscope — a thin tube outfitted with a fiber optic camera and surgical tools. This allows your surgeon to see inside your knee during the procedure.

The surgeon will first remove your torn ACL and clean the area. They will then drill small holes into your tibia and femur so the bone plugs can be attached with posts, screws, staples, or washers.

Following the attachment of the new ligament, the surgeon will test your knee’s range of motion and tension to ensure the graft is secure. Finally, the opening will be stitched, the wound dressed, and your knee will be stabilized with a brace. The length of the surgery will vary depending on the experience of the surgeon and if additional procedures are performed (such as, meniscal repair), among other factors.

Typically, you can go home the day of your surgery.

Because ACL reconstruction is a surgical procedure, it carries certain risks, including:

  • bleeding and blood clots
  • continued knee pain
  • disease transmission if the graft comes from a cadaver
  • infection
  • knee stiffness or weakness
  • loss of range of motion
  • improper healing if the graft is rejected by your immune system

Young children with ACL tears run the risk of growth plate injuries. Growth plates allow bones to grow and are located at the ends of bones in the arms and legs. Growth plate injuries can result in shortened bones.

Your doctor will evaluate these risks when deciding if surgery should wait until your child is older and their growth plates have formed into solid bone.

ACL reconstructive surgery remains the gold standard for repairing this common knee injury. The AAOS reports that about 82 to 90 percent of ACL reconstruction surgeries yield excellent results and full knee stability.

Rehabilitation is key to the success of ACL reconstruction.

Immediately after surgery, you’ll be advised to take pain medications, keep your incision clean and dry, and rest. Icing your knee is extremely important as it helps alleviate pain and decreases swelling. You’ll most likely have a follow-up appointment with your doctor or surgeon within a few weeks of surgery.

Here’s what to expect following ACL surgery:

  • some pain
  • restricted activity for several months
  • walking with crutches for up to six weeks
  • wearing a knee brace for at least one week

You can expect to regain range of motion in your knee within a few weeks after surgery. Athletes typically return to their sports within six to 12 months.

Once the surgery has been deemed successful, a physical therapy regimen can begin. The success of such therapy varies from person to person.