What is anterior cruciate ligament (ACL) surgery?

ACL surgery is the surgical reconstruction or replacement of the anterior cruciate ligament (ACL) in the knee. The thighbone (femur), shinbone (tibia), and patella (kneecap) meet to form your knee joint. Ligaments connect these bones to each other. Your ACL is one type of knee ligament. It is a band of tough, fibrous connective tissue that stabilizes your knee.

Injuries requiring reconstruction or replacement of the ACL are common, especially among athletes. ACL surgery can help restore pain-free range of motion, stability, and function to a knee joint after ACL injury.

ACL surgery is a common but major surgery with risks and potential complications. You may have less invasive treatment options. Consider getting a second opinion about all of your treatment choices before having ACL surgery.

Types of ACL surgery

Injured or torn ACLs do not heal well by sewing the ligament back together. Instead, ACL surgery uses a connective tissue graft to reconstruct or replace your injured ACL. Both ligaments and tendons are connective tissues. Your body heals around the graft over several months. 

The types of ACL surgery procedures include:

  • Allograft reconstruction. An allograft is a piece of cadaver connective tissue, usually a tendon. Allografts come from a tissue bank. Allograft reconstructions require only one incision and cause less pain than an autograft fusion. However, there is a small risk of serious infection, including HIV and hepatitis.
  • Autograft reconstruction. An autograft is a piece of your own connective tissue. Doctors usually take an autograft from a piece of the patellar (kneecap) tendon. This is the gold standard for ACL autograft reconstruction. Your patellar tendon will heal itself and re-grow the missing portion over time. Other autograft sites are your hamstring and quadriceps tendons. These sites do not heal as reliably as your patellar tendon. An autograft requires an additional large incision, lengthens surgery time, and causes more post-operative pain than allograft reconstruction. 
  • Synthetic or artificial graft reconstruction. Artificial ligament graft materials have been studied in trials but have not performed as well as human tissue grafts. Synthetic grafts are still experimental at this time.
  • Xenograft reconstruction. A xenograft is a piece of connective tissue taken from non-human animal sources. Medical scientists are currently conducting human trials of xenograft reconstructions.

Other procedures that may be performed

Your doctor may recommend one or more procedures in addition to ACL surgery:

  • Meniscectomy is the surgical repair or trimming of a torn meniscus. Your knee has two menisci. They are made of cartilage and function as shock absorbers for your knee joint.
  • Other ligament reconstructions. Your knee contains four ligaments including your ACL. Other knee ligaments may also need reconstruction depending on your injury.
  • Patellar realignment is the surgical repositioning of the kneecap.
  • Synovectomy is the surgical removal of part of an inflamed synovial membrane. Synovial membranes are tissues that line joints, including your knee. 

Why is anterior cruciate ligament (ACL) surgery performed? 

ACL surgery is a major surgery that reconstructs or replaces a torn anterior cruciate ligament (ACL) in your knee. Your doctor may only consider ACL surgery for you if it suits your needs and lifestyle. 

Your doctor may recommend surgery to treat complete ACL tears for: 

  • Active adults who want to return to heavy labor or sports that require pivoting, turning, twisting, or hard sideways movements of the knee
  • Combined injuries when other knee injuries are present with an ACL tear 
  • Older children or teens whose growth plates have closed. ACL surgery carries a risk of damaging the growth plate in younger children. This can lead to growth problems. Your child’s surgeon may recommend delaying or modifying ACL surgery to lower the risk of growth plate damage.
  • Symptoms of functional instability including knee pain or a knee that gives way during daily activities. This increases the risk of more knee damage.