Whilst hamstrings remains the most common injury on the AFL injury database, and concussion is certainly the most concerning and significant injury to be managed, the ACL injury is still a diagnosis that is dreaded due to the longer term nature of the injury, and surgery that is so commonly required. The “curse of the ACL” has been very well documented over the past few weeks at AFL level: anyone who follows footy closely would surely have felt enormous disappointment for West Coast’s Nic Natanui upon learning that he had ruptured the ACL in his “good knee”, only just a few games into his return from a reconstruction on his other limb. And even just this week there has been some inspiring stories of comebacks from Sydney’s Alex Johnson (returning after 5 knee reconstructions) and Collingwood’s Tyson Goldsack (returning after just 22 weeks).

In this 3 part series on the ACL, we are going to look at some of the statistics about ACL injuries, the risk of not only occurrence bur also re-occurrence, and discuss some of the latest research guiding ACL rehabilitation protocols.

Firstly, what is the ACL? The ACL (Anterior Cruciate Ligament) sits deep inside the joint knee, partnering with the PCL (Posterior Cruciate Ligament) to provide stability of the knee. The role of the ACL is most critically to limit rotation of the knee but also to limit hyper extension (over straightening) of the knee. The ACL is placed under most strain when the knee is rotating and decelerating, with the foot planted firmly on the ground. This is why the sports with high degree of direction change, speed, and landing forces – AFL and netball to name two – have high incidences of ACL injuries.

Some Interesting ACL Statistics & Beliefs:

• Contrary to popular thought, the vast majority of ACL injuries don’t actually involve any contact. Up to 80% of ACL injuries are actually non-contact and simply involve the athlete landing at speed whilst instantaneously pivoting or changing body direction. Whilst not in the “contact” category, it is not uncommon to see an ACL injury when an athlete is unexpectedly knocked out of position whilst in mid-air, landing whilst trying to decelerate and change position.

• The incidence of ACL rupture in post puberty females is 2-8 times greater than in same age males. There are a few theories for this, which we will discuss later. The peak incidence of ACL injuries in females is 14 – 18 years old, whilst in males is 19- 25 years old. The annual growth rate of ACL injuries has been shown to be almost 9% in girls and 8% in boys.

• The rate of surgical ACL Reconstruction (ACLR) in Australia is significantly higher than in many other countries: 90% of ACL ruptures in the athletic population are operated on in Australia whilst only 50% are operated on in Scandinavia (where some of the latest research is coming from). In the 15 years up to 2015, a staggering 200,000 ACL reconstructions had been performed in Australia.

• One of the justifications for ACLR (other than thinking it was necessary to get an athlete back to sport) was to prevent the onset of Osteo-arthritis (OA) years down the track – a knee without an ACL was thought to be “unstable”, therefore having more internal shear forces, which would slowly erode the joint cartilages, resulting in OA. This is not actually the case, and history has shown that following an ACL rupture, the knee can be up to 10 times more likely to develop OA years later, reconstruction or no reconstruction!

• You need an ACL to return to high level sport! Or do you? Once again, the statistics tell a tale – whilst approximately 90% of ACLR athletes return to some sport, only 50% historically have returned to their pre injury level of sport (the same level/grade of competition they were playing before their reconstruction),and only 44% actually returned to competitive sport. So, an ACLR is not a guarantee! In fact, studies are showing that 40-50% of young adults with isolated ACL ruptures (< 35 years old; no other major ligament/cartilage damage) can cope without the ACL for 5-10 years post injury. It is worth noting that this applies to the non-elite population, which again we will discuss in the next blog.

• An ACL Reconstruction is a 12 month injury! Or is it? This is another controversial topic in ACL rehabilitation, and one which really has no exact answer. In Wednesday’s herald Sun we read about Collingwood’s Tyson Goldsack hopeful return to playing this weekend, only 21 weeks after his reconstruction surgery. And then the very next day we read about Sydney’s Alex Johnson return this weekend also to senior football – after 2236 days of rehab, 5 reconstructions and 12 knee operations overall in a four year period. Whilst traditionally thinking a player could not return to sport for 12 months, we now know that each individual person must be taken on his/her merits and continually assessed for readiness for return to sport. Whilst 12 months is still the overall general aim, we know that the ACL graft doesn’t mature/strengthen for up to three years. One thing we do know for sure is that returning to sport prior to 9 months is highly risky, with the stats showing every month you delay return until the 9 month mark, you reduce your chance of re-injury by 51%.

• The recurrence rate of ACL ruptures (rupturing the reconstructed graft) is around 12-15% but has been shown to be as high as 20%. That’s a reasonably significant figure. And even in the AFL where the medical care, knowledge base and time spent on rehab is world class, the recurrence rate is between 10 – 15%. What is fascinating (not if it happens to you) is the statistic that tells us that if you suffer an ACL rupture in one knee, you are actually an 8-16% chance of going on to rupture the ACL in your good knee: this is the Nic Natanui statistic – going through the long and seemingly perfect rehab only to return to sport and rupture the ACL in your opposite knee. In younger athletes studies have shown that the recurrence rate is even higher – 30% of young people (mean age 17 in this particular study) who returned to sport following ACLR suffered a recurrence of ACL rupture within 2 years, and in another study 25% (mean age 16) suffered a repeat injury within 12months.

So there you go – some pretty sobering statistics surrounding what is traditionally thought to be an extremely successful operation. So is the news all bad – no way! The great thing about statistics is it’s all in the past, and we learn from these great studies and evolve our treatment strategies to meet this latest evidence. There’s enormous upside for those seeking advice on ACL injuries: better knowledge from brilliant studies, improved surgical techniques, new rehabilitation protocols and procedures, understanding of time frames involved, and new preventative exercise programs that are showing results and statistics as exciting as the previous statistics were alarming!

More of all of that in the next blog!

Anthony Lance
SSPC Physiotherapist

References: available on request