What is the Anterior Cruciate Ligament?
Anyone who follows sports such as soccer, AFL, NRL, rugby union, skiing, basketball and a number of other sports involving twisting, turning, jumping, landing and tackling will have undoubtedly heard of players suffering from an ACL rupture. You will also be aware that this injury, the subsequent surgery and the necessary rehab requires their favourite players to be sidelined for anything between 9-12 months but what is the ACL….
The Anterior Cruciate Ligament is one of 2 ligaments (along with the less well known Posterior Cruciate Ligament or PCL) found inside the knee joint that forms a cross (hence the name cruciate) between the shin bone (tibia) and the thigh bone (femur) and give the knee joint much needed stability. The ACL’s 2 main job is to stop the forward translation of the tibia on the femur as well as rotational stability and it actually gives the knee 90% of its stability.
How is the ACL injured?
It is estimated that 70% of all ACL injuries occur through non contact mechanisms (see video below), while the remaining 30% result from direct contact with another player or object. The mechanism of injury is usually associated with deceleration combined with twisting, side stepping manoeuvres, awkward landings or out of control play.
Rate of incidence
During an ACL injury, the injured person may report they heard a “click”, “pop” or “clunk”. They may or not complain of pain in their knee with a potential reduction in their ability to bend or in particular, straighten their knee. What is almost certain with an acute ACL rupture is that they will not be able to weight bear on the injured leg and if they try, they can often experience a “giving way” or “buckling” of their knee with increased pain. Anecdotely, a really common phrase I have heard from patients with suspected ACL injuries is that they don’t “trust” their injured knee.
From a physios perspective, there is a myriad of tests that can be performed to confirm a suspected diagnosis of an ACL injury but a lot of the times in these acute injuries, they can be inconclusive due to the associated swelling and muscle spasm post injury. In reality, the best way to accurately diagnose or rule out an ACL injury is through an MRI scan (or to a marginally lesser degree a CT scan).
MRI scan- pricing and what to expect
Now here’s a little known money saving tip for anybody who suspects that they may have an ACL injury and their health professional recommends they get an MRI scan. Typically, an MRI scan can range in price from $250 upto $400. However, currently if your GP refers you through medicare with a suspected internal derangement of the knee i.e. ACL, PCL or cartilage (known as meniscus) injury you will only have to pay the gap which is usually around $90.
Although MRI scans are the gold standard of scanning, I always make sure I warn people about the process as it doesn’t suit everyone. Firstly, the patient will be asked to undress to their underwear and put on a gown and then they will be asked to lie down on the MRI conveyer belt before they are moved into the tight circular tube of the MRI machine. The main complaint that people have is of a feeling of claustrophobia as they have to lie completely still for 20-45 minutes depending on the area of the body being scanned. Furthermore the defening noise of the MRI noise was quite off putting too.
MRI results & the next step
Following confirmation of a ruptured ACL, the priority is to get the patient into an orthopaedic knee surgeon as soon as possible to try and get ACL reconstruction organised if you have made the decision to go down this route. Secondly, you must get the swelling down and quadriceps muscle function good enough to be ready for surgery.
Now, just to clarify- an ACL rupture is elective surgery not emergency surgery as it is possible to function without an intact ACL in one leg with the appropriate rehabilitation. An older less active person may decide that they want to do this but for someone young, who has an active lifestyle, the ACL reconstruction is the best option in my opinion.