What is the ACL?

The Anterior Cruciate Ligament is a ligament in the center of the knee between the medial wall of the lateral femoral condyle and the anterior central tibia.
It is about 3cm long and has nerve and blood supply.

What is the function of the ACL?

The ACL prevents the tibia from sliding forward and twisting relative to the femur. It ensures optimal biomechanics when we suddenly change direction and put abnormal rotatory forces on the knee.
The ACL contains nerve fibres that feedback to the muscles around the knee to activate a response to the abnormal load on the knee. So, if you step and twist the knee the ACL senses that and your muscles relax or contract to pull you and your knee straight.

Is the ACL the only important ligament in the knee?

The Anterior cruciate ligament is one of 4 major ligaments in the knee. The other major ligaments are the medial collateral ligament (MCL), the lateral collateral ligament (LCL) and the Posterior Cruciate Ligament (PCL).
We also have complexes or smaller ligaments that provide secondary stability to rotation – these include the Posterolateral complex, posteromedial complex, and anterolateral complex.

What is the meniscus?

We have 2 menisci – the medial and lateral menisci.
The meniscus is semicircular cartilage that is positioned between the femur and tibia. The menisci are attached to the tibia by very strong attachments called roots.
The menisci are very important to share the load between the femur and tibia and protect the articular cartilage.
They also have a secondary role to give stability to the knee amongst other roles.
It is important to try to preserve as much meniscus as possible for as long as possible.

How does the ACL get injured?

The Anterior cruciate ligament (ACL) may be injured by a number of different mechanisms. A strong blow to the outside of the knee, a twisting injury of the knee or a hyperextension injury of the knee.
Different people with different anatomy requires a different amount of force in order to tear the ACL.
The ACL may be injured along with other structures in the knee. The most common structures injured at the same time as the ACL are the menisci and less commonly the medial collateral ligament (MCL). There is almost always bruising of the bone of the femur and tibia and the overlying articular cartilage.
In very high force injuries, one may damage almost all the structures at the same time.

Do ACL tears heal?

No… but…
The ACL is designed to fit perfectly into the space allocated to it. Usually, the ACL is injured with a high energy mechanism in which case the ligament “explodes”. The 2 ends of the ligament are usually apart and don’t heal together. Sometimes one of the ends heals onto the posterior cruciate ligament (PCL) and this may provide some stability but often not enough to get back to high demand sports.
Very occasionally, a low energy injury causes the ACL to tear off a bone attachment usually the femur. This may also be a partial tear. Some cases like these, where the structural integrity of the ligament remains may heal or may be amenable to repair rather than reconstruction (see below – but to be discussed with your doctor).

What happens if I leave my ACL not fixed?

You are going to put more stress on your menisci and articular cartilage!
Well actually it depends on what you want to do and whether your ACL has stuck down to anything else.
If you are able to strengthen your muscles and limit your activity you may be able to cope. Some studies have shown that this is possible.
Many other studies, however, have shown that the longer time you spend playing pivoting sports without an ACL the more chance you have of damaging your meniscus. When you damage your meniscus, you put your general joint health at risk.

What is a pivoting sport?

This is anything where you have to stop and/or change direction suddenly. You may even pivot when you running on uneven ground.

High-Risk sports include but are not limited to:

  • Soccer
  • Rugby
  • Netball/korfball
  • Hockey
  • Skiing
  • Tennis
  • Trail Running


ACL reconstruction is surgery to replace a torn anterior cruciate ligament which is one of the major ligaments in your knee.  ACL injuries most commonly occur during sports that involve sudden stops and changes in direction such as soccer, rugby, netball/korfball, hockey, skiing, tennis, and trail running.

In ACL reconstruction the torn ligament is replaced with part of a tendon taken from another area of your knee.  The surgery is carried out through an arthroscopic procedure using small incisions around your knee.

ACL reconstruction is best performed by an orthopaedic surgeon who is experienced in knee surgery.


Ligaments are strong bands of tissue that connect one bone to another.  They help protect against abnormal movement and control the normal movements of the knee.  The ACL is one of two ligaments that cross in the middle of your knee connecting your thigh bone (femur) to your shin bone (tibia) and helps stabilize your knee joint.

Most ACL injuries happen during sports that can put stresses on the knee:

  • suddenly slowing down and changing direction (cutting)
  • pivoting with your foot firmly planted
  • landing incorrectly from a jump
  • stopping suddenly
  • receiving a direct blow to the side or the front of the knee


Although conservative treatment with good rehabilitation can suffice for some patients who are not particularly active in sports it is generally recommended that surgery is carried out for patients who:

  • are young and active
  • want to go back to rotational sports
  • have instability of their knee with normal daily activities
  • have concomitant injuries such as collateral ligament damage or meniscus tears.

The need for you to have surgery should be discussed with your surgeon.


Before the operation:

You may likely undergo some weeks of physiotherapy in order to reduce the pain and swelling and to ensure that your knee has got a good range of movement and your muscles are strong before the operation.  If you have surgery when your knee is still inflamed, swollen, and doesn’t have the full movement you may not regain a full range of movement after the surgery.

The surgery:

This is usually carried out as a one day or overnight procedure.  It is done with the use of an arthroscope where small holes are made in the knee through which the surgeon works to place the new ligament in position.  Small holes will be drilled through the shinbone and the thigh bone in order to pass the ligament and it is then fixed to bone securely.

The surgery normally takes around an hour and is done with a spinal and general anaesthetic that prevents post-operative pain.

The surgeon will choose which graft is most suitable for your particular injury and will use either hamstring tendon; quadriceps tendon; or patella tendon to reconstruct your ACL.

After the procedure, you will be in a brace that will be used for between four and six weeks depending on your injury and surgery.  You will have a physiotherapy treatment prior to leaving the hospital so that you know how to walk correctly and look after your knee and manage the brace. You will get an appointment for a wound check and stitch removal.

Off work:

You should take 7-10days off to rest the knee, but you won’t be able to do manual labour for 4-6 weeks.


Your physiotherapist will help you regain movement and start with certain strengthening exercises.  Once you reach a certain stage of your rehabilitation a biokinetist will take over the strengthening and re-education of your muscles.

This is absolutely essential for the good recovery and success of your operation.


Generally, it takes a minimum of 9 months for the knee to be fully rehabilitated and strong.  However, it is often recommended that patients wait a year before returning to their chosen sport.


Risks of surgery

  • Infection

All surgery has a risk of infection but in our unit, this is less than 1% and we take all necessary precautions.

  • Clots in the leg (deep vein thrombosis)

The risk is also low, less than 1%

  • Stiffness

This is a very rare complication where patients lose the ability to fully bend or straighten their knees and with good pre-op and post-operative rehabilitation, this is a low-risk factor.

  • Numbness

Occasionally, about 5%, of patients get a little loss of feeling around the incision where the graft was taken.

  • Failure of the graft

The graft can stretch out through no one’s fault and the knee can become unstable.

In about 5-7% of cases, the graft can get torn in sports or with sudden rotational movements, as happened with your original ACL injury.

To see a video of ACL procedure, please visit
Patient info

We ensure that quality care is afforded to our patients even before formal consultation by taking necessary information about our patients, their lifestyle, and their current ailments.

Knee Specialists in Johannesburg

Prof. Ponky Firer, Dr. Brad Gelbart, and Dr. Matthew Street specialize in knee conditions of any type. Their approach is to improve your mobility and lessen your pain in the least invasive manner possible.

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