Anterior cruciate ligament (ACL) reconstruction

Your health expert: Mr Henry Maxwell, Consultant Orthopaedic Surgeon
Content editor review by Pippa Coulter, February 2022
Next review due February 2025

Anterior cruciate ligament (ACL) reconstruction is a type of knee surgery to replace one of the main ligaments in your knee. You may be offered this surgery if your ACL is injured. It can help to get your knee working properly again.

An image showing the different parts of the knee

About ACL reconstruction

Your ACL connects your thigh bone to your shin bone and helps to keep your knee stable. If you’ve torn or sprained your ACL, ACL reconstruction can replace the damaged ligament with a graft. This is a replacement tendon from another part of your knee. It’s usually done as a keyhole procedure. This means your surgeon will carry out the operation through tiny holes in your skin, rather than needing to make a larger cut.

Not everyone with an ACL injury needs surgery. But your doctor may be more likely to recommend surgery if:

  • you play sports that include a lot of twisting and turning – such as football, rugby or netball – and you want to get back to it
  • you have a very physical or manual job – for example, you’re a firefighter or police officer or you work in construction
  • other parts of your knee are damaged and could also be repaired with surgery
  • your knee gives way a lot (known as instability)

It’s important to think about the risks and benefits of surgery and to talk this through with your surgeon. They’ll discuss all your treatment options and help you to consider what would work best for you.

Your surgeon will also explain exactly what to expect before, during and after the procedure, and any risks involved. Take your time before deciding, and make sure you ask your surgeon if you have any questions. If you decide to go ahead with the procedure, you’ll need to sign a consent form. This is why it’s important to make sure you feel properly informed.

Preparing for ACL reconstruction

Preoperative rehabilitation (prehabilitation)

Your surgeon is unlikely to proceed with your ACL reconstruction before any swelling has gone down and you’ve got strength and movement back in your knee. This might be within a couple of weeks after your injury, but it varies from person to person. They’ll usually ask you to follow a preoperative rehabilitation programme during this time. This may include:

  • exercises designed to strengthen your leg muscles
  • exercises to improve your range of motion
  • general light activities such as walking and swimming

Getting ready for surgery

Your surgeon will explain what else you need to do to prepare for your operation. For example, if you smoke, you’ll be asked to stop because smoking increases your risk of getting a chest or wound infection, and slows healing time.

You’ll usually have the surgery as a day case, which means you won’t need to stay overnight. You may have it under general or spinal anaesthesia. If you have a general anaesthetic, this means you’ll be asleep during the operation. If you have a spinal anaesthetic, you’ll stay awake but the lower part of your body will be numb. Sometimes, you may have a sedative with spinal anaesthesia to help you relax. This may also make you feel drowsy, so you might not remember much about your operation. You’ll need to arrange for someone to drive you home and stay with you overnight.

You’ll usually be given a time to stop eating and drinking before your operation. Follow the advice from your hospital and if you have any questions, just ask.

At the hospital

On the day of your procedure, your surgeon will meet with you to check you’re well and still happy to go ahead. Your healthcare team will do any final checks and get you ready for surgery. They may ask you to wear compression stockings or have an injection to help prevent deep vein thrombosis (DVT).

What happens during ACL reconstruction?

ACL reconstruction usually lasts between one and three hours.

The procedure is usually done by keyhole (arthroscopic) surgery. This means it’s carried out using instruments inserted through several small cuts into your knee. Your surgeon will use an arthroscope – a thin, flexible tube with a light and camera on the end of it – to see inside your knee.

After examining the inside of your knee, your surgeon will remove the piece of tendon to be used as a graft. The graft is usually a piece of tendon from another part of your knee, for example:

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

Your surgeon will then create a tunnel through your upper shin bone and lower thigh bone. They’ll thread the graft in through the tunnel and fix it in place, usually with screws or staples. 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.

Image showing ACL reconstruction

What to expect after ACL reconstruction

After your operation, you’ll need to rest until the effects of the anaesthetic have passed. You’re likely to have some pain, stiffness and discomfort as the anaesthetic wears off, but you'll be offered pain relief as you need it. You’ll be encouraged to get up and move around, and to put weight on your leg as soon as possible. You may be given crutches and a knee brace to help support you.

You’ll usually be able to go home once the anaesthetic has worn off. But you’ll need someone to drive you home and stay with you overnight. You’ll have dressings over the wounds around your knee.

Before you go home, your nurses will give you advice about caring for your healing wounds. They’ll also talk to you about any possible complications to look out for, such as signs of infection or deep vein thrombosis (DVT). For more information on these, see our section on complications below. They’ll also discuss pain relief you can take at home. They may give you a date for a follow-up appointment, including any physiotherapy sessions you will need.

Having a general anaesthetic can make you feel very tired. You might find that you're not so co-ordinated or that it's difficult to think clearly. This should pass within 24 hours. In the meantime, don't drive, drink alcohol, operate machinery or make any important decisions.

Recovering from ACL reconstruction

It usually takes about six months to a year to make a full recovery from ACL reconstruction.

You’ll see a physiotherapist within the first few days after your operation. They’ll give you a rehabilitation programme with exercises specific to you. This will help you to get the full strength and range of motion back in your knee. You’ll usually have a series of goals to work towards. This will be very individual to you, but a typical ACL reconstruction recovery timeline may be similar to this:

  • 0–2 weeks – building up the amount of weight you can bear on your leg
  • 2–6 weeks – beginning to walk normally without pain relief or crutches
  • 6–14 weeks – full range of motion restored – able to climb up and down stairs
  • 3–5 months – able to do activities such as running without pain (but still avoiding sports)
  • 6–12 months – return to sport

The exact recovery times vary from person to person and depend on many things. These include the sport you play, how severe your injury was, the graft used and how well you’re recovering. Your physiotherapist will ask you to complete a series of tests to see if you’re ready to get back to sport. They’ll want to check that you feel mentally ready to return too.

During your recovery, you can continue to 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 because ice can damage your skin.

Your surgeon will be able to advise you about when you can return to work, driving, and other activities.

Complications of ACL reconstruction

Most people recover well from ACL reconstruction. But any surgery carries a risk of complications. The possible complications of any operation include things like infection, excessive bleeding, developing a blood clot or having an unexpected reaction to the anaesthetic.

The main complications specific to ACL reconstruction are listed here.

  • Your knee might keep on giving way (instability). This may happen if there’s a problem with the placement of your graft.
  • You might continue to feel stiffness and your knee might not move as well as it did before. This may be caused by arthritis or arthrofibrosis (when scar tissue forms in your knee joint).
  • You may continue to feel pain in your knee.
  • You might get problems in the area where the graft was taken from – for instance, your kneecap.
  • You may get a tear in your graft and need further surgery.

Your risk of complications may be higher if you have other problems with your knee. These include an injury to the meniscus (cartilage) in your knee.

Alternatives to ACL reconstruction

The alternative to having ACL reconstruction surgery is to continue with physiotherapy. You may find this is enough, especially if you’re not planning to do high-level sports or activities. Your doctor may also suggest measures such as wearing a knee brace during weight-bearing exercise to protect your knee. You can also decide to delay surgery and see how you get on with physiotherapy first. People who decide to have surgery later on seem to do just as well as people who have surgery within a few weeks of their injury.

Looking for physiotherapy?

You can access a range of treatments on a pay as you go basis, including physiotherapy.

To book or to make an enquiry, call us on 0370 218 6528

If you have an ACL injury, your knee is likely to be very swollen and painful. You may hear or feel a ‘pop’ when the injury happens, and you may feel as if your knee might give way. You won’t be able to move your knee as much and you may find it difficult to stand and walk. Seek urgent medical advice if you have these symptoms.

ACL reconstruction uses grafts from your patellar tendon or your hamstring. Research shows there’s very little difference between the two in terms of how well your knee functions. Overall, there’s no best graft. This will be individual to you and is something your surgeon will discuss with you.

Yes, you will be encouraged to put weight on your leg and to move around as soon as possible. You may need crutches to support you at first. But you should expect to be walking normally after a couple of weeks. For more information, see our sections on aftercare and recovery above.

You have an ACL reconstruction under general or spinal anaesthesia, so you won’t feel any pain during the operation. But you are likely to have some pain after the operation. You can take painkillers to help manage this. For more information on this, see our section on aftercare above.

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