ACL reconstruction surgery can help restore mobility and stability to the knee following a severe injury. These injuries include tearing and are more common in athletes.

The anterior cruciate ligament (ACL) is one of four major ligaments in the knee. It helps keep the knee stable and moving properly.

Athletes of high impact sports, such as football, have an increased risk of tearing their ACL. When a tear occurs, a person may need surgery to restore mobility and increase stability in their knee.

This article reviews what ACL reconstruction surgery is, when people need it, what happens during the procedure, and what recovery from surgery is like.

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The ACL is one of four major ligaments in the knee that help provide support and stability. The others include the:

The ACL runs in a diagonal direction between the femur and the tibia, two bones that meet at the knee. Its primary job is to prevent the tibia from slipping in front of the femur. It also helps keep the knee stable when it moves from side to side.

A tear to the ACL often occurs with injury to other structures in the knee, such as the articular cartilage, meniscus, or other ligaments. Tears can range in severity from mild to severe or complete tears of the ACL.

Surgery can help repair the ACL and allow it to heal. This will increase the stability and mobility of the knee joint again.

The procedure itself involves placing a tendon graft onto the ACL. A surgeon generally cannot repair a torn ACL using sutures or stitches as other types of ACL injuries might be.

Read more about ACL injuries.

People with a complete tear will typically require ACL reconstruction surgery to regain the function and stability of the knee.

Experts generally recommend the following groups undergo the surgery:

  • active adults involved in sports or physically demanding jobs
  • young children and teens with ACL tears
  • those with combined injuries to other areas of the knee
  • those with high instability in the knee that may injure other areas of the knee as a result

Read more about torn ACLs.

Prior to the procedure, a person will have an intravenous (IV) line put in their arm. The IV allows the surgical team to provide anesthesia, sedatives, or other medications during the procedure.

Once the surgeon selects the graft tissue, they will either surgically remove it from the person’s body or use a sample prepared from a cadaver. They then outfit the tendon with anchor points to graft the tendon into the knee during surgery.

When ready, the surgeon will make a small incision in the front of the knee to insert an arthroscope. This is a thin tube that contains a fiber-optic camera and surgical tools.

The surgeon will first remove the torn ACL and clean the area. Next, they will drill small holes into the tibia and femur, so they can attach the bone anchors with posts, screws, staples, or washers.

Once attached, the surgeon will test the knee’s range of motion and tension to ensure the graft is secure.

Finally, the surgeon will close the opening with stitches, dress the wound, and stabilize it with a brace.

A person will typically go home the same day as the procedure.

Prior to ACL reconstruction, a person may need to undergo several weeks of physical therapy to improve their surgical outcome. This is due to swelling and stiffness that occur immediately following the injury, limiting a person’s range of motion. Once the person gets their full range of motion, a surgeon can typically perform the surgery. Having full range of motion prior to surgery helps to improve the outcome.

A doctor may also recommend a person spend time with a brace to help protect the ligaments in the knee. This gives the other ligaments time to heal, so a surgeon may only need to fix the ACL.

Prior to the procedure, a doctor will typically recommend a final examination. This checks for other areas of issue that may require repair during the surgery.

A person will often get specific instructions from a surgical team. It is important for a person to follow all directions regarding when to arrive for surgery, when to stop eating or drinking, or what medications they can safely take.

It is also important to tell the surgeon about any preexisting conditions, so they can better prepare for possible complications.

Following surgery, a person will almost certainly require physical therapy or other forms of rehabilitation to regain strength, mobility, and stability in their knee.

To start, a doctor will likely prescribe pain medications to help with post-surgical pain. They may also recommend icing the knee to help keep pain and swelling down.

A surgeon will likely schedule a follow-up appointment a week or more after the surgery. This can help the doctor determine if the knee is healing properly and check for infections at the incision site.

A person will typically be on activity restrictions for a few weeks following the procedure. They will likely slowly return to activities and require bracing and crutches during recovery for up to a few weeks after surgery.

Full recovery and return to sports or other activities can take between 6–12 months.

When combined with physical therapy, ACL reconstruction is generally well-tolerated and successful. Most people can return to sports within the first year following the procedure.

People tend to have the best success rate following the surgery with physical therapy and exercises. According to the National Health Service (NHS), approximately 80% of people regain full function of the knee after ACL reconstruction surgery.

As with all surgeries, ACL reconstruction surgery has some risks for the person undergoing the procedure.

Some common ones associated with ACL reconstruction include:

  • blood clots
  • numbness
  • stiffness
  • bleeding
  • instability of the knee
  • viral transmission
  • infections at the site of the incision
  • growth plate injury
  • extensor mechanism failure — or failure of other tendons — or fractures of the patella

Long-term effects may include a risk for osteoarthritis, chronic pain, and a decreased range of motion.

Anterior cruciate ligament reconstruction surgery uses a graft of tendons to replace the ACL and restore function to the knee. Doctors generally recommend it for those with severe or compound injuries, athletes or those who work physically demanding jobs, and younger people.

The surgery is generally successful, particularly when combined with rehabilitation therapies, such as physical therapy.

A person should discuss all potential risks and recovery requirements with a doctor.