ACL Surgery: Overview

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The anterior cruciate ligament (ACL) is one of four primary ligaments that provides stability to the knee joint. If the ACL is torn, surgery may be needed to restore knee function. ACL surgery (also called ACL reconstruction) involves replacing the torn ligament with a piece of tendon called a graft. While this surgery is generally considered safe, it's best to be informed about potential complications, as well as the extensive rehabilitation process required after surgery.

Senior female patient in discussion with doctor during check up in exam room

Thomas Barwick / Getty Images

What Is ACL Surgery?

ACL surgery is performed by an orthopedic surgeon in an outpatient surgical center or hospital under general or regional (spinal) anesthesia. The surgery may be done in adults and children, and it is usually completed in less than two hours. 

ACL surgery entails reconstructing the ligament using a tendon graft. The type of graft used depends on factors like:

  • The surgeon's preference
  • The patient's age
  • Whether there are associated knee injuries

Oftentimes, an autograft is used, which means the tendon is taken from the patient's own body. Types of autografts used for ACL surgery include:

  • Patellar (knee) tendon
  • Hamstring (back of the thigh) tendon
  • Quadricep (front of the thigh) tendon

Sometimes, an allograft (a tendon from a deceased donor, called a cadaver) is used to reconstruct the torn ACL.

Research suggests there is no benefit to using one type of graft versus another. An exception is that allografts may have an increased risk of failure in young athletes, so these are generally reserved for patients age 35 and older.

Various Surgical Techniques

Most ACL surgeries are performed arthroscopically. This means that a small camera and other long, thin surgical instruments are inserted through multiple small incisions in the knee joint. Less commonly, open surgery is performed in which a large incision is made in the knee.

The two main arthroscopic techniques used to reconstruct the ACL include:

  • Single-bundle reconstruction: The ACL is connected to the femur (thigh bone) on top and the tibia (shinbone) below. With this conventional technique, bone tunnels are first drilled into these two bones. The ACL graft is then pulled through the tunnel and fixated in the same location as the torn ACL with a device, often a screw.
  • Double-bundle reconstruction: The ACL actually consists of two bundles of fibers. With this newer technique, two smaller grafts (instead of one larger tendon graft) are used to reconstruct each ACL bundle. This technique may take a little longer since two additional bone tunnels need to be made in order to pull through and secure the second graft.

There is debate over which technique leads to better outcomes. While some research suggests that the double-bundle technique enhances the stability of the knee joint and provides better knee functionality, other research reveals no difference in terms of knee stability and function. More long-term data is needed.


Contraindications to undergoing ACL surgery include poor overall health and a lack of motivation to complete the intensive rehabilitation program required after surgery.

Older age is not necessarily a contraindication. In fact, research has found that patients over 60 years who are active and don't have knee arthritis generally have good outcomes from undergoing ACL reconstruction.

Purpose of ACL Surgery

The purpose of ACL surgery is to restore function of the knee. Left untreated, a knee with a torn ACL may have ongoing symptoms of knee instability. This is usually a sensation of buckling or the knee "giving out." For some people, this may not be bothersome, but for others, it may interfere with their activities.

There are no standard guidelines for determining who should (or shouldn't) undergo such surgical repair. Instead, multiple factors are considered when making this decision.

Surgery tends to be favored in patients who:

  • Are young and active
  • Participate in certain sports: For example, sports that involve pivoting, jumping, or rapid acceleration/deceleration, such as soccer, basketball, or lacrosse
  • Are high-profile athletes
  • Have other knee injuries besides a torn ACL (e.g., medial collateral ligament injury)
  • Experience significant knee instability

In the end, making a decision to have ACL reconstructive surgery can be difficult. The procedure itself is not the only factor that needs to be considered, as the rehabilitation after surgery lasts a number of months and full activity may be restricted up to a year.

How to Prepare

Once your ACL surgery is scheduled, your surgeon will provide you with various pre-operative instructions.

  • Wear loose comfortable clothing, especially pants, on the day of your surgery.
  • Stop eating after midnight on the eve of your surgery.
  • Stop certain medications for a period of time before your surgery (for example, blood thinners like aspirin).
  • Practice using crutches, since you will use them after surgery.
  • Arrange to have someone drive you home after surgery.

Your surgeon may also recommend that you work with a physical therapist to perform various exercises prior to your procedure. This may help optimize your functional outcome after surgery.

What to Expect on the Day of Surgery

On the day of your ACL surgery, you will first be taken to a pre-operative room where the following events will occur:

  • You will be asked to change into a gown.
  • A nurse will place an IV in your hand for delivering fluids and medications.
  • Members of the surgical and anesthesia teams will come in to talk with you about the surgery.

Next, you will be taken into the operating room where you will be given anesthesia medications to put you to sleep.

Your ACL surgery (using the traditional single-bundle technique) will then typically proceed with the following steps:

  • Your surgeon will make two to three small incisions (cuts) around the knee.
  • Through these incisions, an arthroscope and other surgical instruments will be inserted into the knee joint. The surgeon will view live images of the inside of the knee being projected onto a screen by the camera attached to the arthroscope.
  • Next, if an autograft is being used, your surgeon will make a four-centimeter incision to remove or "harvest" a portion of a tendon from another part of your body.
  • The graft obtained will be cleaned and trimmed to ensure the correct size, and then set aside and stored in a designated tissue freezer.
  • The torn ACL will then be removed with a motorized shaver so that the new graft can be placed.
  • Since the new ACL needs to be attached to the bone above and below the knee joint, a drill will be used to make bone tunnels through the thigh and shin bones.
  • The graft is then pulled through the bone tunnels and secured with hardware, such as screws, posts, or staples.
  • The surgical instruments will then be removed and the incision sites will be stitched or taped.
  • A bandage will then be placed over the surgical site.

After the surgery, you will be taken to a recovery room.


In the recovery room, a nurse will monitor your vitals, ensure your pain is under control, and provide you with post-operative instructions from your surgeon.

Once you are stable (typically after about two to three hours), you will be discharged and your friend or family member can drive you home.

For your immediate recovery after surgery (10 to 14 days), your surgeon will likely recommend the following instructions:

  • Ice your knee regularly to reduce swelling and pain.
  • Take your pain medication as prescribed.
  • Keep the bandage over your wound clean and dry.
  • Use crutches to keep weight off of the leg that was operated on.
  • Wear a brace and use a continuous passive motion (CPM) machine for your knee, if recommended (based on surgeon preference).

Typically, you can expect to return to work within a few days to weeks, depending on the nature of your job, and begin driving again after around two weeks after surgery (sometimes sooner).

Since rehabilitation is an absolutely essential component to recovery, you will also start attending regular physical therapy sessions soon after surgery.

Long-Term Care

Patients who undergo ACL surgery will need to remain motivated and committed to an extensive and long-term rehabilitation program.

Key goals of rehabilitation after surgery include:

  • Minimizing knee swelling
  • Maintaining mobility of the kneecap
  • Achieving full range of motion of the knee
  • Strengthening the quadriceps and hamstrings
  • Restoration of leg control and balance

In the majority of cases, patients who undergo ACL reconstruction continue to have a stable knee even 15 to 20 years after surgery.

Potential Risks

As with any operation, complications may occur with ACL surgery.

Some possible complications include:

  • Limited knee range of motion and stiffness
  • Knee pain
  • Numbness near the surgical incision site
  • Infection
  • Damage to the nerves or blood vessels around the knee
  • Problem with the tendon graft (e.g., re-tearing or loosening)
  • Blood clots in the leg
  • Growth plate injury in children or adolescents

A Word From Verywell

An ACL injury is the most common type of sports injury to the knee. If you or a loved one has been diagnosed with an ACL tear, it's important to have a thoughtful discussion with a trusted and experienced orthopedic surgeon. Keep in mind that not all ACL injuries require surgery. In some cases, rehabilitation alone may be the right decision for you.

17 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading

By Jonathan Cluett, MD
Jonathan Cluett, MD, is board-certified in orthopedic surgery. He served as assistant team physician to Chivas USA (Major League Soccer) and the United States men's and women's national soccer teams.