Patient Education

Anterior Cruciate Ligament

The anterior cruciate ligament (ACL):
connects the tibia (shin bone) to the femur (thigh bone).

The function of the ACL
  • -Is to provide stability to the knee and minimize stress across the knee joint.
  • -It restrains excessive forward movement of the lower leg bone (the tibia) in relation to the thigh bone (the femur).
  • -It limits rotational movements of the knee.

There are number of nerves within the ACL which act as sensors that provide the brain with information about joint position sense (proprioception). When,
for example, the ACL is stretched this information forms part of a "feedback mechanism" to activate certain protective muscle actions.

Mechanism of injury:

The ACL is particularly prone to injury during sporting activities that involve significant amounts of twisting and turning, such as skiing and football.

This injury is usually due to a sudden stop and twisting motion of the knee, or a force or "blow" to the front of the knee. The extent of the tear can be a partial
or a complete tear. It is often injured together with other structures inside the knee joint. [Cartilage or other ligaments]

Impact of ACL injury :
  • -When the ACL is damaged as part of a twisting injury the patient may hear or feel a "popping" sensation.
  • -As the ligament has a blood supply, when torn, the knee fills with blood becoming swollen quite quickly and painful.. [Haemoarthrosis].
  • -Patients with injured ACL can find it very difficult to return to any sports that require twisting and turning, such as, rugby, football, squash and skiing. However,
    other "in line" sports such as running, cycling or cross training are often possible, despite ACL deficiency. In general, it is almost impossible to continue sporting activity after acute ACL rupture and urgent medical review is required.


Most patients with injured ACL have the following symptoms:

  • -Swelling within a few hours of the injury.
    -Loss of Motion [Loss of ability to extend and flex the knee].
  • -Distinctive "pop" heard
  • -Giving-way" episodes. Your knee may collapse and you fall to the ground .
  • -Pain with activity.
  • -Some people are able to continue their activity; some people's knees collapse and they cannot walk normally .
  • -Knee "catching" or "locking".

Diagnosis of injury to the ACL :

As with all surgical conditions, diagnosis of damage to the anterior cruciate ligament is made by a combination of:

  • listening to the patient's history .
  • Clinical examination .
  • use of modern imaging techniques e.g. MRI scan .

Treatment of ACL injuries :

Treatment decisions for ACL tears are always individualized. The decision whether to offer surgery is based on the person's age, activity level, how unstable
the knee is, and whether other structures in the knee have been injured. Unfortunately a simple surgical repair by suturing the torn ligament together is not effective. A successful repair involves completely replacing the torn ligaments (surgical reconstruction), and there are a number ways that this can be done.

ACL Reconstruction Surgery

Usually surgical reconstruction is recommended to restore stability to allow people to return to desired activities and to prevent secondary damage to the menisci (cartilage cushions) and articular cartilage of the knee, hopefully avoiding premature deterioration of the knee. All our ACL reconstruction surgery is done arthroscopically.

We prefer reconstruction using an autograft [tissue graft harvested from the patient] rather using allograft [ cadaveric tissue] asI believe tissue from the patient results in a better reconstruction with superior long term results and lower ACL re injury rates.

Due to advances in surgical techniques, this has turned what was a major open operation to one that is now minimally invasive (via arthroscopic portals). As indicated, there are a variety of different techniques available, but surgeons have their own preferences based on their own experience and results.

The Surgery:

ACL reconstruction involves undergoing a general anaesthetic and an in-patient stay of one night. The operation itself lasts for just over an hour and a tourniquet is applied to the leg during the procedure. The operation is carried out under direct vision of the arthroscope (camera) inserted within the knee through key-holes. A bony tunnel is drilled within the shin bone (tibia) and the thigh bone (femur) to allow the graft to be pulled across and held in place securely.

After Surgery:

Any surgical procedure has possible risks and complications. Surgeons make every effort to minimize them. They include:

  • -Deep Venous Thrombosis (DVT) or Blood clots
  • -Infection
  • -Stiffness

In the immediate post-operative period, the priority is:

  • -muscle-strengthening.
    -to regain the range of motion

The post-operative programme:
  • -Crutches and a brace are provided for a two-week period, but you will be able to stand unsupported.
  • -Physiotherapy begins the day of surgery.
  • -The sutures are removed from the wounds after two weeks.
  • -You should be able to easily bend the knee to a right angle the day next to the surgery.
  • -You are expected to be able to cycle and run within three months following surgery.
  • -The speed of recovery from this operation is limited by the ability of the body to integrate the graft material into the bony tunnels and to become fixed. This integration takes a minimum of ten weeks, but the graft itself is not "mature"/strong enough for participating in contact sports for at least six to nine months.