ACL reconstruction surgery is a surgical procedure to restore the function of a torn ACL (anterior cruciate ligament). There are four main stabilizing knee ligaments – the anterior, posterior, medial collateral, and lateral collateral ligaments. The ACL ligament is deep within the knee, connecting the femur (thigh bone) to the tibia (shin bone). It provides stability by preventing the tibia bone from moving too far forward relative to the femur.

ACL Tear Mechanism

How does an ACL tear occur? When we think of ACL tears, we often think of football, but any sudden pivoting or change-of-direction activity can tear an ACL, as can landing awkwardly after a jump. Sometimes, a tear happens when the knee is struck forcefully from the side.

Some people sense or even hear a ‘pop’ when the ligament tears, and they may fall to the ground or find it very difficult to bear weight. The knee will typically start to swell (because of bleeding into the knee) briskly, and while some people experience pain, others experience little or no pain. Most people, however, will know that something significant has happened to the knee or that the knee feels unstable.

Most ACL tears have an accompanying injury. Around 60% of people who tear their ACL will also have injured a meniscus, but many people will also have tearing of another ligament, such as the medial collateral ligament (MCL), or damage to the articular cartilage lining the joint.

ACL tears are more common in females, and female athletes are 4-5 times more likely to suffer an ACL tear than male athletes. There are many reasons for this, including:

  • Anatomy: Women have a smaller notch in the femur, which the ACL passes through, and the smaller the notch, the bigger the risk of ACL tears.

  • Hormones: ACL tear risk increases when estrogen concentrations are higher during the menstrual cycle’s late follicular and ovulatory phases.

  • Muscle Development: Women typically have less developed hamstrings and glutes than men, which means less ACL protection when landing or pivoting.

What About Partial ACL Tears?

Many people wonder if a partially torn ACL can repair itself or if it requires surgical repair. Generally speaking, if the knee is stable, then a trial of physio rehabilitation is a good option.

Should I Have ACL Surgery?

ACL reconstruction surgery isn’t for everyone. Many people with low athletic demands on their knees or those who are much older do very well with conservative rehabilitation, such as physio and strength work. I do my very best to help guide my patients through this decision-making process by deeply understanding their needs. The decision is very much a joint decision.

If you regularly play sports that involve jumping or twisting, if your occupation is physically demanding, if your knee regularly gives way, or if other structures in the knee are also damaged, we may decide that ACL reconstruction is for you.

Graft Options

In the UK, most grafts used in ACL reconstruction are hamstring grafts. Still, as a knee surgeon, I believe it’s important to be able to offer different surgical options to suit the needs of the individual rather than a ‘one size fits all’ operation. This is why I have trained to be able to provide different reconstruction options, not merely a hamstring graft.

When I meet a patient with an injured knee, I want to understand the person’s activity levels and occupation, their lifestyle and expectations, and even their ability to undertake the necessary rehabilitation where surgery is to be considered.

Patella Tendon Grafts (aka Bone-Patella Tendon-Bone Graft)

The surgery is carried out under a general anesthetic, so you will be asleep. I make a vertical incision over the front of the knee, and the middle third of the patella tendon is removed along with a small piece of bone from the patella (above) and tibial bone (below). There is a bony plug at each end of the patella tendon. I then make a tunnel through the tibial and femoral bones, and the graft is passed through the tunnel; I use metal screws to fix the graft in place, and the incisions are stitched closed. A cold compression device/cuff will be applied to your knee to help with pain and swelling. The whole procedure takes around an hour and a half, and after the surgery, you’ll be taken to a recovery area while you gently wake up. A little later, you will be seen by a physiotherapist who will take you through some early exercises, and when you’re ready, you’ll be able to go home.

Most patients who have had ACL reconstruction will be able to fully weight-bear post-surgery and won’t require bracing, but sometimes if I’ve also repaired a meniscus or carried out surgery to the articular cartilage, I may ask you to wear a brace and toe-touch weight bearing for a few weeks.

Why Use a Patella Tendon Graft?

Patella tendon grafts are strong grafts, and they became popular for treating professional athletes, especially younger athletes in their teens and early twenties, because the re-tear rate in that age group is lower using patella tendon grafts than hamstring tendon grafts.

A few people experience persistent anterior knee pain after a patella tendon ACL reconstruction, which may be more common for women with particularly small kneecaps. Kneeling on the knee may sometimes feel uncomfortable. To mitigate these risks, we use bone grafts to fill in the defect, but a study has shown a small increase in the risk of anterior knee pain when patella tendon graft ACL reconstruction is compared with hamstring tendon ACL reconstruction. The flip side is that the reconstruction is a robust procedure and may be the right choice for athletic younger patients participating in demanding sports such as football and rugby.

Quadriceps Tendon Graft ACL Reconstruction

Why Use a Quads Tendon for ACL Reconstruction?

Quads tendon grafts are twice as thick as patella tendon grafts, and hamstring grafts (which consist of the gracilis and semitendinosus tendons) must be doubled over to make a graft of four tendon strands. Even when all four hamstring strands are bundled together, they are typically smaller in collective cross-section than a quads tendon.

Because a section of the patella bone isn’t removed with a quads tendon graft, patients are less likely to suffer from anterior knee pain compared to patella tendon graft patients. Kneeling is also likely to be more comfortable after surgery, and achieving full knee extension (an important first stage of recovery) may be easier too.

If a patient has had a medial collateral ligament (MCL) tear in addition to their ACL tear, I prefer to carry out a quads tendon graft ACL reconstruction to preserve the hamstring. This is because hamstring grafts are harvested from the medial side of the hamstring, and the hamstring is important for providing medial stability to the knee. Using a quads tendon graft means we can avoid having to use the all-important medial hamstring tendons.

This surgery is a day-case surgery, and you will be asleep during the procedure. A temporary nerve block is also administered to the knee so you will wake up and feel comfortable. I make two ‘portal’ holes at the front of the knee to permit a camera and instruments to be passed through the knee.

The graft is harvested via a small horizontal incision from the area of the quads tendon just lateral to the vastus medialis oblique where the tendon is the thickest. After the tendon is harvested, I repair the quads tendon. I make holes in the femoral and tibial bones to receive the graft, and the graft is secured in place with specially designed buttons and metal screws. A cold compression device/cuff will be applied to your knee to help with pain and swelling. After you have woken up in recovery, you will return to a ward and be seen by a physiotherapist. When you are ready, you will be able to go home.

Hamstring Tendon Grafts

Most ACL reconstructions in the UK are carried out using a hamstring graft. The choice of the graft to use influences the risk of a re-tear, but as we age, the risk of re-tear when we compare quads tendon, hamstring tendon, and patella tendon grafts becomes the same. When we consider allograft ACL reconstruction surgery, re-tear remains a little higher. The risk of a re-tear is small but is highest in people under 22, and as we age, our risk of re-tear lessens over time, although the reason for this isn’t entirely understood.

What Happens During a Hamstring Graft ACL Reconstruction?

This is a day case procedure, so you will usually be in and out of the hospital on the same day. You’ll have a general anesthetic, so you’ll be asleep and won’t feel any pain during the procedure. The first step is to make a small incision on the inner side of your knee to remove a portion of your semitendinosus hamstring tendon. I use a special technique for preparing the graft and will only need to use one of your hamstring tendons. Occasionally, this tendon is too small, so I may have to use the gracilis tendon as well.

The tendon is then prepared to create a graft to serve as your new ACL. Next, I make a few small incisions around your knee joint and insert a tiny camera called an arthroscope. This allows me to see inside your knee joint and assess any damage. I’ll remove any damaged tissue and prepare the bone for the graft placement.

To secure the graft in the correct position, I’ll drill small tunnels through the femoral and tibial bones and then thread the graft through these tunnels, ensuring it’s in the same position as your natural ACL.

Once the graft is in place, I’ll secure it tightly using specially designed buttons and metal screws to ensure it is stable. After that, I’ll close the incisions with sutures and skin glue, and the wound will be covered with a transparent dressing. A cold compression device/cuff will be applied to your knee to aid control pain and swelling.


Allograft may be an option if you are older than 40 years old, as the re-tear rate is similar to autograft (patient’s own tissue) with an easier recovery as I don’t need to take your tissue as a graft for your new ACL. However, it is not recommended for young patients due to the higher re-tear rate. If you have received an allograft, you are not allowed to donate blood.

Women and ACL Reconstruction

We know that female athletes are three times more likely to rupture their ACL ligament than male athletes, and re-tear rates are higher for women who’ve had a hamstring graft ACL reconstruction. Women athletes tend to be quads dominant, leading to quads/hamstring mismatch. Hamstring works in synergy with the ACL by providing anterior stability (stopping your knee moving forwards). By taking hamstring tendons, it further worsens this mismatch. A quads tendon graft may be the best option for you as a woman athlete (to preserve your hamstring and avoid taking your patella tendon, as women tend to have smaller kneecaps).

Is the ACL Reconstruction Likely to Re-Tear?

The good news is the risk of your ACL reconstruction re-tearing is low – around 6%:

Research shows that if you’re under 22 and very active, the re-rupture rate is twice as likely in a hamstring graft than with a patella tendon graft.

There are also other factors contributing to re-tear rates, such as knee laxity (hyperextension), pivoting sports, and other associated injuries such as meniscal tear.

You can calculate your re-tear rate following ACL reconstruction using this calculator: ACL Re-Injury Risk Calculator

LET (Lateral Extra-Articular Tenodesis)

If you’re under 25 years old and play pivoting sports, I will recommend adding LET to your ACL reconstruction. A landmark research in 2020 showed at least a 60% reduction in the risk of graft re-tear following ACL reconstruction in high-risk patients.

LET involves making a small scar on the lateral (outside) of your knee and using a strip of your iliotibial band to reinforce your knee, providing additional rotational stability and protecting your ACL graft.

What’s the Recovery Like After an ACL Reconstruction?

Before embarking on ACL reconstruction, it’s important to understand that it’s a lengthy journey that begins before the surgery. It’s important that you have some prehabilitation (prehab) before the surgery to get your knee into the best possible condition. This has been shown to improve outcomes after surgery, and I recommend a period of 6 weeks from the time of the injury to get plenty of physio to reduce swelling and improve quads and hamstring strength.

Getting the best out of your operation takes commitment and help from a skilled physiotherapist. It’s a 9-12 month journey for most patients who want to return to sport, but you can do a great deal early on.

After the operation, most patients can fully weight-bear, but if you’ve also had a meniscal repair or other ligament repair, you may need to use crutches for a few weeks to support the knee while it heals. Physio starts immediately, and you’ll need to make time to carry out the rehab exercises.

If you drive an automatic car and have had surgery on your left knee, you can start driving a few days post-surgery, providing you can drive the car safely. If you’ve had surgery on your right knee, or if you drive a manual car, you’ll need to be able to carry out an emergency stop before you can drive. This may take 4-6 weeks.

Your occupation will determine how much time you need to take off from work, and it’s important that you don’t rush back – after all, you’ll need to be able to have the time to focus on your rehab. I recommend taking two weeks off work if you have a desk-based job and then working from home until you’re mobile (if you can), and you may need two to three months if you’re on your feet a great deal for work.

The initial rehab goals are to achieve a full range of movement, particularly extension, in your knee and to strengthen your quads muscles. Your physio will progress your rehab slowly, increasing your strength, proprioception skills, and power so that you can eventually return to your preferred activities and sports.

As a rough guide, if you are strong enough, you may be able to expect to return to some gentle running at around 4 months. To be able to do this, you need to have no swelling in the knee, have a full knee extension, and have passed some performance movement tests set by your physio. Returning to sport, especially pivoting sports such as football, may take 9-12 months.

Book an appointment

Contact the clinic today on 0115 9662 174

Schedule a consultation to discuss your treatment options and find the best solution for your knee pain.