Our Health Library information does not replace the advice of a doctor. Please be advised that this information is made available to assist our patients to learn more about their health. Our providers may not see and/or treat all topics found herein.
Anterior Cruciate Ligament (ACL) Surgery
Surgery for anterior cruciate ligament (ACL) injuries reconstructs or repairs the ACL.
- ACL reconstruction surgery uses a graft to replace the ligament. The most common grafts are autografts using part of your own body, such as the tendon of the kneecap (patellar tendon) or one of the hamstring tendons. Sometimes the quadriceps tendon from above the kneecap is used. Another choice is allograft tissue. This is taken from a deceased donor.
- Repair surgery typically is used only in the case of an avulsion fracture. (This is a separation of the ligament and a piece of the bone from the rest of the bone.) In this case, the bone fragment connected to the ACL is reattached to the bone.
ACL surgery is usually done by making small incisions in the knee and inserting small tools for surgery through these incisions (arthroscopic surgery). In some cases, it is done by cutting a large incision in the knee (open surgery).
In reconstruction of a partial or complete tear of the ACL, the best time for surgery is not known. Surgery that's done right away after the injury has been linked with increased fibrous tissue leading to loss of motion (arthrofibrosis) after surgery.footnote 1 Some experts believe that surgery should be delayed until the swelling goes down, you have regained range of motion in your knee, and you can strongly contract (flex) the muscles in the front of your thigh (quadriceps).footnote 1 Many experts recommend starting exercises to increase range of motion and regain strength shortly after the injury.
In adults, age isn't a factor in surgery, but your overall health may be. Surgery may not be the best treatment for people with medical conditions that make surgery a greater risk. These people may choose nonsurgical treatments. And they may try to change their activity levels to protect their knees from further injury.
Many orthopedic surgeons use arthroscopic surgery rather than open surgery for ACL injuries because:
- It makes it easy to see and work on the knee structures.
- It uses smaller incisions than open surgery.
- It can be done at the same time as diagnostic arthroscopy (using arthroscopy to find out about the injury or damage to the knee).
- It may have fewer risks than open surgery.
How It Is Done
Bone and knee tissue graft
For anterior cruciate ligament (ACL) surgery, the replacement graft can be harvested from tissue in the patellar (kneecap) region. The surgeon removes the tissue along with a small piece of bone called a "bone block" at each end. The graft is first pulled through the two tunnels that were drilled in the upper and lower leg bones and then secured with screws or staples.
For anterior cruciate ligament (ACL) surgery, the replacement graft can be harvested from up to three tendons. The surgeon uses part of the tendon from the semitendinosus muscle and part of the tendon from the gracilis muscle. The graft is pulled through tunnels that were drilled in the upper and lower leg bones. Then the graft is secured with screws or staples.
What To Expect
Arthroscopic surgery is often done on an outpatient basis. This means that you don't spend a night in the hospital. Other surgery may require staying in the hospital for a couple of days.
You will feel tired for several days. Your knee will be swollen. And you may have numbness around the cut (incision) on your knee. Your ankle and shin may be bruised or swollen. You can put ice on the area to reduce swelling. Most of this will go away in a few days. You should soon start seeing improvement in your knee.
To care for your incision while it heals, you need to keep it clean and dry and watch for signs of infection.
Physical rehabilitation after ACL surgery may take several months to a year. How long it takes to return to normal activities or sports is different for every person. It takes most people at least 6 months to return to activity after surgery.footnote 2
Why It Is Done
The goal of ACL surgery is to:
- Restore normal or almost normal stability in the knee.
- Restore the level of function you had before the knee injury.
- Limit loss of function in the knee.
- Prevent injury or degeneration to other parts of the knee.
Not all ACL tears need surgery. You and your doctor will decide whether rehabilitation (rehab) only or surgery plus rehab is right for you.
You may choose to have surgery if you:
- Have completely torn your ACL or have a partial tear and your knee is very unstable.
- Have gone through a rehab program and your knee is still unstable.
- Are very active in sports or have a job that requires knee strength and stability (such as construction work), and you want your knee to be as strong and stable as it was before your injury.
- Are willing to complete a long and rigorous rehab program.
- Have chronic ACL deficiency. This means that your knee is unstable and affects your quality of life.
- Have injured other parts of your knee, such as the cartilage or meniscus, or other knee ligaments or tendons.
You may choose not to have surgery if you:
- Have a minor tear in your ACL. (This type of tear can heal with rest and rehab.)
- Are not very active in sports and your work doesn't require a stable knee.
- Are willing to stop doing activities that require a stable knee or stop doing them at the same level of intensity. You may choose instead to do other activities that don't require a stable knee, such as cycling or swimming.
- Can complete a rehab program that stabilizes your knee and strengthens your leg muscles to reduce the chances that you will injure your knee again, and you are willing to live with a small amount of knee instability.
- Do not feel motivated to complete the long and rigorous rehab program you would need after surgery.
- You have medical problems that make surgery too risky.
How Well It Works
A few people who have ACL surgery still have knee pain and instability and may need another surgery (revision ACL reconstruction). Revision ACL reconstruction is generally not as successful as the initial ACL reconstruction.
ACL reconstruction surgery is generally safe. Complications that may arise from surgery or during rehabilitation (rehab) and recovery include:
- Problems related to the surgery itself. These are uncommon but may include:
- Numbness in the surgical scar area.
- Infection in the surgical incisions.
- Damage to structures, nerves, or blood vessels around and in the knee.
- Blood clots in the leg.
- The usual risks of anesthesia.
- Problems with the graft tendon (loosening, stretching, reinjury, or scar tissue). The screws that attach the graft to the leg bones may cause problems and require removal.
- Limited range of motion, usually at the extremes. For example, you may not be able to completely straighten or bend your leg as far as the other leg. This is uncommon, and sometimes another surgery or manipulation under anesthesia can help. Rehab attempts to restore a range of motion between 0 degrees (straight) and 130 degrees (bent or flexion). It's important to be able to get your knee straight so you can walk normally.
- Grating of the kneecap (crepitus) as it moves against the lower end of the thighbone (femur), which may develop in people who did not have it before surgery. This may be painful and may limit your athletic performance. In rare cases, the kneecap may be fractured while the graft is being taken during surgery or from a fall onto the knee soon after surgery.
- Pain, when kneeling, at the site where the tendon graft was taken from the patellar tendon or at the site on the lower leg bone (tibia) where a hamstring or patellar tendon graft is attached.
- Repeat injury to the graft (just like the original ligament). Repeat surgery is more complicated and less successful than the first surgery.
- Honkamp NJ, et al. (2010). Anterior cruciate ligament injuries in adults. In JC DeLee et al., eds., Delee and Drez's Orthopaedic Sports Medicine: Principles and Practice, 3rd ed., vol. 2, pp. 1644–1676. Philadelphia: Saunders Elsevier.
- Micheo W, et al. (2015). Anterior cruciate ligament tear. In WR Frontera et al., eds., Essentials of Physical Medicine and Rehabilitation, 3rd ed., pp. 324–330. Philadelphia: Saunders.
Current as of: July 1, 2021
To learn more about Healthwise, visit Healthwise.org.
© 1995-2021 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.