What is ACL?
ACL is the short name for a ligament of the knee called Anterior Cruciate Ligament. Ligaments are tough, chord-like structures, which connect bones. There are four such ligaments in the knee - one on the inner side, one on the outer side, and two in the middle. The two middle ligaments cross each other, and are called cruciate ligaments. Of these, the one in front is called Anterior Cruciate Ligament or ACL.

What happens if ACL is torn?
The usual history involves twisting injury of the knee followed by pain and swelling. Often, a cracking sound is heard. The patient may experience that his knee moved in an odd way. X-rays are usually normal, and hence this injury is often considered a ‘minor’ sprain. The patient may feel ‘normal’ for a long time, before his knee starts feeling unstable. It is only at this stage that the ligament injury is diagnosed.

Feeling of instability of the knee prevents one from rigorous activities such as running, jumping etc. Once torn, ACL does not heal. People with a low-level of physical activity may be able to manage despite a ruptured ACL, but in others the knee feels weak. One may feel unsure of the knee, or the knee may give-way. Each episode of ‘giving-way’ causes further damage to the knee by rupturing the meniscus (cushions). This, in turn, causes injury to the soft caps covering the bones and the cartilage. The natural squeal of such continuing insult to the knee is early wear and tear of the knee (osteoarthritis), which becomes a source of constant pain and swelling.

MRI is one way to confirm the diagnosis of a torn ACL. Often, it is not possible to differentiate a partial tear from a complete tear. Clinical examination, followed by arthroscopic viewing, is the only sure way of diagnosing a torn ACL.

What are the different ways of treating an ACL deficient knee?
Exercises: Not all knees with a torn ACL need surgery. In patients with low levels of physical activity, treatment with physiotherapy may ‘tune’ the knee to control itself. Nearly 80% of these patients lead a normal life, and may not feel the need to go for surgery.

Reconstruction of ACL: If a patient’s body does not adapt to a torn ACL, the only option is to make a new ligament (reconstruction), which is done by replacing the torn ligament with a substitute (graft). The graft is taken from the tendons of the knee and fixed where the original ligament was. With time, the ‘new ligament’ gets incorporated in the knee, and functions somewhat like the original ligament.

How is ACL reconstructed?
ACL reconstruction is done by two methods: open surgery or key-hole (arthroscopic) surgery. Today, arthroscopic surgery has become the preferred operation. The operation consists of the following steps:

A diagnostic arthroscopy to confirm the diagnosis and take stock of the damage.
Graft harvested from the knee.
Graft prepared to fit as a ligament.
Tunnels are drilled in the bone to pass the graft into the knee

The graft is fixed at the two ends. All this is done arthroscopically, without opening the knee. There are minimum scars with this method.

The technique of arthroscopic ACL reconstruction is constantly evolving. The basic differences in all the available techniques are as follows:

(a) The source of the graft: The graft may be taken from the knee-cap tendon (patellar tendon) or from the tendons at the back of the knee (Hamstring tendons).
(b) Single or double incision: Graft fixation at two ends can be done through two separate incisions or one incision.
(c) The fixation devices used: A host of fixation devices are used to fix the graft. These are made of metal or self-dissolving plastic.

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