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Anterior cruciate ligament (ACL) reconstruction

Anterior cruciate ligament (ACL) reconstruction is a type of knee surgery to replace the ACL, usually using a tendon from another part of your body.

Tying up laces on trainers

ACL injury

The ACL is a band of fibrous tissue that helps to stabilise your knee. You can tear or sprain your ACL – it’s one of the most common knee injuries. Most of them (around seven out of ten ACL injuries) happen when playing sports. Injury usually happens when you slow down very quickly while turning or sidestepping at the same time. Some sports that are particularly prone to causing ACL injury are basketball, netball, rugby, football and skiing.

You can find more information on ACL injury including causes and symptoms on our Bupa knee clinic.

Who needs ACL reconstruction?

If you’ve torn your ACL, your doctor is likely to suggest a reconstruction if your knee is unstable (gives way) and you:

  • previously played a lot of sport and want to get back to it
  • have an active job, which involves heavy lifting or where it would be unsafe to have an unstable knee, for example roofers, or people in the military or police force
  • have other damage to your knee

If you have knee injuries that mean you’re at risk of osteoarthritis later in life, then your surgeon may also s

Alternatives to ACL reconstruction

Physiotherapy, exercise and support

Some people with an ACL tear may not need an operation to repair it. You may have physiotherapy, exercises and a hinged knee brace to give your knee support. Your doctor may suggest this type of treatment if:

  • your knee is stable
  • you have partially torn your ligament, rather than fully torn it
  • you’re older and don’t play sports or do physical activities that place a lot of strain on your knees

Delayed reconstruction

ACL reconstruction isn’t always done straightaway. You can still have an operation many months later if your knee doesn’t recover well enough with physiotherapy and an exercise regime. About four out of ten people treated this way will not need an operation. Those who do still need surgery have results that are just as good as those operated on within a few weeks of their injury.

Whether you have immediate surgery depends on:

  • whether you have other knee injuries that need surgical repair
  • how quickly you need to get back to sporting activity or work

For more information, speak to your doctor. They’ll be best placed to advise which treatment options are most suited to your individual situation and needs.

Preparation for ACL reconstruction

Your surgeon may delay the operation to allow any swelling to go down as much as possible and any stiffness in your knee to be resolved. It’s best if you have a pain-free, full range of movement in your knee by the time you have surgery. Otherwise, the result may not be as good as it could be.

Your operation is likely to be at least three weeks after your injury, but this varies from person to person. Your surgeon may ask you to have physiotherapy during this time. As well as making sure you can move your knee as fully as possible, exercises will help:

  • to reduce swelling
  • to strengthen surrounding muscles
  • your recovery after surgery

Your surgeon will explain how to prepare for your operation. For example, if you smoke, you’ll be asked to stop. Smoking increases your risk of getting a chest and wound infection, which can slow your recovery. You may also be asked to stop taking the contraceptive pill, as it can increase your risk of blood clots.

Cuts and scratches below the knee can increase your risk of getting an infection after surgery. So your surgery may be delayed until they’ve healed. This is why your surgeon may ask you to stop shaving your legs up to six weeks before your operation.

You may have your operation under a general anaesthetic or an epidural (spinal anaesthetic). If you're having a general anaesthetic, you’ll usually be asked to follow fasting instructions. This involves not eating or drinking for a set amount of time before your surgery. It’s important to follow your surgeon’s advice. You’ll usually be asked to stop eating six hours before your operation, but can drink water up to two hours before.

Your surgeon and anaesthetist will talk to you about your procedure beforehand. They’ll answer any questions you have and tell you what to expect. Do ask any questions you’d like answered so you understand what will happen. It may help to have a list of questions ready to ask. Once you’re happy that all your questions have been answered, you sign a consent form, giving your permission for the procedure to go ahead.

Bupa's online knee clinic

What happens during an ACL reconstruction?

ACL reconstruction is carried out with a general anaesthetic or a spinal anaesthetic. If you have a general anaesthetic, this means you’ll be asleep during the operation. These days, this type of surgery is often done as a day case, so you don’t go to hospital until the day of the surgery and go home the same day.

Before the operation, you’ll meet your surgeon to discuss your care. It may differ from what’s described here as it will be designed to meet your individual needs.

After you have had the anaesthetic, your surgeon will examine your knee to check how badly your ligament is torn and if any other tendons or ligaments have been damaged. Although they’ll have examined your knee before, it’s easier to do a very thorough examination when you are completely relaxed.

ACL reconstruction is keyhole surgery, meaning it’s done through several small cuts. Your surgeon will make these cuts in the skin over your knee. They’ll use an arthroscope – a thin, flexible tube with a light and camera on the end of it to see inside your knee. This is known as knee arthroscopy.

ACL reconstruction involves replacing your torn ligament with a graft. In ACL, a graft is usually a piece of tendon that is put in place of the injured ACL. It acts as scaffolding for a new ligament to grow along.

Your surgeon will first, remove the piece of tendon to be used as the graft.

The graft is usually made from part of a tendon in another part of your knee, for example:

  • hamstrings, which are tendons at the back of your thigh
  • the patellar tendon, which holds your kneecap in place

Sometimes surgeons use a graft from a donor. This is called an allograft and will be collected before your surgery. You’re most likely to have a donor graft if you’re having further surgery to an ACL repair. You can find out more about grafts used in ACL reconstruction in our FAQs below.

Your surgeon will then drill a tunnel through your upper shin bone and lower thigh bone. This means the graft can be put in almost the same place as your damaged ligament. They’ll put the graft into the tunnel, attach it to your bones and fix it in place, usually with screws or staples. These are normally left inside your knee permanently. Before finishing the operation, your surgeon will make sure there is enough tension on the graft and that you have full range of movement in your knee. Then they’ll close the cuts with stitches or adhesive strips.

Your operation will usually last between one and three hours.

Image showing ACL reconstruction 

What to expect afterwards

This operation is often done as a day case. This means you’ll be able to go home after the anaesthetic has worn off. If you’ve had a general anaesthetic, you may need to stay in hospital overnight.

After a local anaesthetic it may take several hours before the feeling comes back into your treated knee. Take special care not to bump or knock the area. It’s best to keep your leg elevated as much as possible. You can have painkillers if you need them.

You’ll have dressings over the small wounds around your knee. Your nurse will advise you about caring for your healing wounds before you go home.

A physiotherapist will come and see you and help you up. They’ll give you crutches and show you how to use them. They may also give you a knee brace to give some support to your joint as it heals, although not all surgeons use these. There isn’t really any evidence that a knee brace will help you to recover after ACL reconstruction or that it will help to prevent further injury. You’re more likely to have one if you have non-surgical treatment for an ACL injury. For information on knee braces and returning to sport, see our FAQs below.

It’s safe to put weight on your leg as soon as you’re able to get up, but it is easier to use crutches to start with.

Your physiotherapist will give you some exercises to do while you recover. The amount of physiotherapy people need varies, so follow the advice of your physiotherapist and surgeon.

Before you go home, you may be given a date for a follow-up appointment.

General anaesthesia temporarily affects your co-ordination and reasoning skills. You must not drive, drink alcohol, operate machinery or sign legal documents for 24 hours afterwards. You’ll need to arrange for someone to drive you home. And you should try to have a friend or relative stay with you for the first 24 hours after your operation.

Recovering from an ACL reconstruction

It usually takes about six months to make a full recovery from ACL reconstruction. But to start with, it’s important not to do too much. Your leg should be up when you’re not moving around or doing your exercises. Avoid too much standing or walking. If your knee starts to swell, you’ve overdone it.

It takes about two weeks after ACL surgery to be able to walk without crutches, fully straighten your leg and bend it to 90 degrees.

If you have a desk-based job, you may be able to go back to work four to six weeks after your operation. This may be sooner if you work part-time. If you have an active job it will take longer – typically between four to six months – but this will depend on exactly how active your job is. It’s important to know how to get back to work after sick leave. If you have an active job, you’ll need to do this gradually. Speak to your surgeon for advice.

Most people are able to go back to playing sport around six months after their operation. This varies from person to person though and will depend on the sport you play and how well you’re recovering. It’s important to follow your surgeon’s advice.

During your recovery, you can take over-the-counter painkillers such as paracetamol or anti-inflammatory medicines, such as ibuprofen. Make sure you read the patient information that comes with your medicine and if you have any questions, speak to your pharmacist for advice. You can also apply ice packs (or frozen peas wrapped in a towel) to your knee to help reduce pain and swelling. Don't apply ice directly to your skin though, as it can damage it.

You won’t be able to drive until your surgeon gives you the go-ahead. Some surgeons will let you drive if your left leg was the one operated on and you have a car with automatic gears. If you're in any doubt about driving, contact your motor insurer for their recommendations, and always follow your surgeon's advice.

You shouldn’t fly on a long-haul flight for at least six weeks after your surgery. Your surgeon may recommend waiting longer, so it’s important to always follow their advice.

Side-effects of ACL reconstruction

All procedures have side-effects, but not everyone has every side-effect to the same degree. After ACL reconstruction you may have:

  • pain
  • swelling and bruising
  • stiffness

You’re likely to have some pain after surgery and your knee may tend to swell during the first six weeks after your operation. For more information about managing pain and swelling, see our Recovery section.

Complications of ACL reconstruction

Complications are problems that occur during or after your operation. The possible complications of any operation include excessive bleeding, developing a blood clot, usually in a vein in your leg (deep vein thrombosis), or having an unexpected reaction to the anaesthetic.

The main complications of ACL reconstruction are listed below.

  • The graft used to repair your ACL may tear (graft failure). This happens in up to six in every hundred patients.
  • You might experience numbness along the outside of your upper leg, near where the surgical cuts were made. This is quite common and can be temporary or permanent.
  • Your knee joint may remain unstable if the graft tears or stretches.
  • There’s a risk of permanent stiffness in your knee, or less movement than you had before your injury (arthrofibrosis).
  • The tendon your graft was taken from may weaken and tear.
  • You might have long-term knee pain, or pain when you kneel down. This can be a problem if the tendon in your knee was used as the graft.
  • It’s possible that you could get an infection. Infection is rare, happening in about one in two hundred people who have ACL reconstruction. You’ll have IV antibiotics at the time of surgery to try and prevent it.

Pros and cons of ACL reconstruction

This information is intended to help you understand the advantages and disadvantages of ACL reconstruction. Think about how important each particular issue is to you. You and your doctor can work together to decide what's right for you. Your decision will be based on your doctor’s expert opinion and your personal values and preferences.


  • Having ACL reconstruction could help to stabilise your knee, relieve pain and reduce the risk of further knee injury.
  • Having ACL reconstruction means you may be able to return to playing sports, such as netball, football, rugby, basketball or skiing.
  • ACL surgery is carried out in a keyhole procedure. It's less invasive than some other forms of surgery. This can result in less time spent in hospital, less pain and a faster recovery.


  • It can take six months to fully recover from ACL reconstruction. If you have an active job, then you may need to take up to six months off work.
  • You have to stick to an exercise regime for several months after your surgery to help you recover.
  • As with all surgical procedures, you might get side-effects and there’s a risk of complications. You could still get pain or stiffness in your knee after surgery.
  • ACL doesn’t work for everyone. You may be left unable to play sport, even if you have surgery.

FAQ: How will I know I've injured my ACL?

If you've damaged your ACL, your knee is likely to be very swollen and painful. Swelling and pain come on suddenly and usually get worse during the first few hours after the injury. Some people also hear a 'pop' when the injury happens.

You may find it difficult to stand and walk, and your knee will either give way or feel like it would give way if you put your weight on it. Movement of your knee may be limited.

ACL injuries normally happen when you're playing sports, though sometimes an injury can develop over time. A tear in your ACL can happen when you slow down suddenly and then twist, sidestep or have an awkward landing. It can also be caused by a blow to the knee, for example, during a rugby tackle or road traffic accident.

If you think you may have injured your ACL, you should visit your GP or the accident and emergency department of your local hospital.

FAQ: Is one type of graft better than the other?

There are two main types of graft available for ACL reconstruction – autografts and allografts. Autografts are tendons taken from your body, allografts come from a donor.

Autografts are usually taken from either:

  • your patellar tendon, which connects your patella (kneecap) and your tibia (shin bone)
  • your hamstring tendons at the back of your knee

There is very little difference between a graft from your patellar tendon or your hamstring. There’s no research that shows that one type of autograft is better than the other.

Allografts are from donors. They are used if you have had ACL reconstruction in the past and it hasn’t worked, or if you have injuries to several ligaments and tendons in your knee. Having this type of graft may mean you're more likely to get an infection, although the risk is still low.

Overall, there’s no ‘best’ graft. They each have their advantages and disadvantages when it comes to treating different people.

Your surgeon will discuss the different options available to you.

FAQ: Should I wear a knee brace after surgery?

Some people wear a knee brace when they return to playing sport. However, they can be bulky and awkward to wear. You don’t need to wear one, but you might find that it helps build your confidence as your knee will feel supported.

Talk to your surgeon about the options available to you and any concerns you have about returning to your usual activities.


  • Cruciate ligament treatment on demand

    You can access a range of our health and wellbeing services on a pay-as-you-go basis, including cruciate ligament treatment.

  • Other helpful websites Other helpful websites

    Further information


    • Knee ligament tears NSCCG. Map of Medicine., published October 2016
    • Acute knee injuries. Brukner & Khan's Clinical Sports Medicine (4th ed. online). McGraw-Hill Medical., published 2012
    • ACL Injury. American Academy of Orthopaedic Surgeons., last updated September 2009
    • Anterior cruciate ligament injury. BMJ Best Practice., last updated October 2016
    • Anterior cruciate ligament injury treatment and management. Medscape., last updated June 2016
    • ACL reconstruction: information for patients. Nuffield Orthopaedic Centre., accessed January 2017
    • Nursing patients requiring preoperative care. Oxford Handbook of Adult Nursing (Online). Oxford Medicine Online., published 2009
    • Knee Arthroscopy. American Academy of Orthopaedic Surgeons., last updated September 2016
    • Anterior cruciate ligament reconstruction. Queen Elizabeth Hospital Birmingham., last updated April 2013
    • Frobell RB, Roos EM, Roos HP, et al. Supplement to a randomized trial of treatment for acute anterior cruciate ligament tears. N Engl J Med 2010; 363:331–42
    • Anterior cruciate ligament pathology treatment and management. Medscape., last updated June 2016
    • Anterior cruciate ligament pathology clinical presentation. Medscape., last updated June 2016
    • Mohtadi NGH, Chan DS, Dainty KN, Whelan DB. Patellar tendon versus hamstring tendon autograft for anterior cruciate ligament rupture in adults. Cochrane Database of Systematic Reviews 2011, Issue 9. Art. No.: CD005960. DOI: 10.1002/14651858.CD005960.pub2
    • Anterior cruciate ligament pathology treatment and management. Medscape., last updated June 2016
    • Kruse LM, Gray B, Wright RW. Rehabilitation after anterior cruciate ligament reconstruction: a systematic review. J Bone Joint Surg Am 2012; 94(19):1737–48. doi:  10.2106/JBJS.K.01246
    • Shaerf DA, Pastides PS, Sarraf KM, et al. Anterior cruciate ligament reconstruction best practice: a review of graft choice. World J Orthop 2014; 5(1):23–29. doi:  10.5312/wjo.v5.i1.23
    • Legnani C, Terzaghi C, Enrico B, et al. Management of anterior cruciate ligament rupture in patients aged 40 years and older. J Orthop Traumatol 2011; 12(4):177–84. doi:  10.1007/s10195-011-0167-6
    • Knee ligament injuries. PatientPlus., last checked February 2017
    • Treuting R. Minimally invasive orthopaedic surgery: arthroscopy. Ochsner J 2000; 2(3):158-63. PMCID: PMC3117522
    • Personal communication, Mr Roger Tillman, Orthopaedic Surgeon, April 2017
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Reviewed by Laura Blanks, Specialist Health Editor, Bupa Health Content Team, April 2017
Expert reviewer Mr Roger Tillman, Orthopaedic Surgeon
Next review due April 2020

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