In the first part of our 3 series ACL blog, we looked at some of the sobering statistics of ACL, and unfortunately between blogs, the “good news story”’ of Sydney’s Alex Johnson returning after 5 knee reconstructions and 12 operations, has ended with him rupturing the ACL in his good knee in his 2nd senior game back!
Today, we’ll go back to a few of the statistics and explain why females are more at risk than males, look at traditional return to sport timeframes following ACL Reconstructions (ACLR), and debate the surgery versus no surgery question.

The Incidence of ACL rupture in post puberty girls is 2-8 times greater than males of the same age

Not only are girls such a high risk of suffering an ACL injury as the above statistic outlines, they are also 33% more likely to suffer a 2nd ACL injury (on their good leg) than males of the same age What makes females so vulnerable to ACL injuries?


Probably the biggest reason we have to explain the high female incidence is anatomical or biological differences! The skeletal structure of females and males is different and the following factors are thought to put females at greater risk:
• Females have a slightly wider pelvis than males, meaning that the thigh bone (femur) meets the knee at a greater angle than it does in boys, and this angle (what we call the Q angle) places greater stress on the ACL.
• Females tend to have a smaller ACL and a smaller notch that the ACL sits in, along with a greater slope to their upper tibial surface, all potentially leaving the ACL vulnerable to rupture.
• There has been some interesting recent research that seems to indicate that the pre ovulatory phase of the menstrual cycle (days 6 – 13) can leave ligament structures in females more vulnerable to injury at this time.
• The normal ratio of hamstring to quadriceps strength is ideally around 60% (eg the hamstring muscle group is 60% the strength of the quadriceps muscle group). Females tend to be more quad dominant than males, meaning this ratio is biased to the quads. The quads tend to place some force on the ACL, which is normally resisted by the hamstrings, so if the quad force is stronger than usual and the hamstring force weaker than usual, this strain on the ACL is increased.
So whilst it all seems despair for females and ACL injuries, it’s not! There are two main strategies that should be introduced at adolescent levels: firstly, neuro-muscular programs (more of this in the final blog) have the goal of improving how athletes jump, land and decelerate, and build a greater defence against the biomechanical factors that leave females at risk. These programs can be simply added to the warm up part of a training regime, and have been shown to reduce ACL injuries by 40-65%. And secondly, targeted strength programs that address particularly hamstring strength and conditioning in female adolescents is crucial.

An ACL Reconstruction is a 12 month Injury – or is it?

Traditionally thought of as a 12 month injury, the ACLR boundaries (like many injury management strategies) have been pushed over recent years to become shorter and shorter. From 12 months, the returns were being aimed at 9-10 months in some sports, and then you get the exceptions: Footscray’s Tony Liberatore who returned successfully in 18 weeks post ACLR, and it was only three years ago that a 7 month return was being predicted in ACL circles as “the norm”. Collingwood’s Tyson Goldsack is currently attempting a return at the 22 week mark!

Within this time the opinions have been many and varied! A LARS (artificial/synthetic graft) has been attempted to aim at a 12 week return, but has failed numerous times and has all but been taken off the market; The push from 12 months down to 7-8 months has shifted back to the conservative 12 month time period. The concerning high number of recurrences in adolescents has seen many experts push for an 18 month to 2 year time frame in younger kids.

Here’s two critical facts we do know for sure:
1. For every month you delay a return to sport after ACLR (up to the 9 month mark) you reduce the risk of re-injury by 51%. What this tells us is that the majority of non-elite athletes, (and certainly younger athletes) having an ACLR should not attempt a return in under 9 months, and quite possibly should be given 12-18 month return to sport timeframes.
2. The ACL graft may still be maturing 2 – 3 years after a reconstruction. There are so many critical factors used to determine if an athlete is ready to return to sport, and MRI to determine graft maturity is not one of them! What we do take from this though, is that in order to return to sport when a graft may not be at its most mature, all the other critical factors (such as strength, hopping ability, neuromuscular control etc) must be addressed in a thorough and intensive rehabilitation.
So it’s not as simple as it seems – the critical factor in considering return to sport time frames (other than age and professional status of the athlete) is has the patient done the rehabilitation necessary to be able to pass the critical return to sport tests that we clinically can assess for?

I need an operation to fix my knee!

Or do you? In Australia, traditionally a ruptured ACL has resulted in a surgical reconstruction. Given the risk of recurrences post ACLR, and the fact that preventing OA is not a reason to have a reconstruction, and the statistic that tells us that only 50% of people return to their pre injury level of sport, more thought has been given to the possibility of conservative (non-operative) management of ACL ruptures. Whilst this could be a whole blog topic on its own, what we can say is that you should have a serious discussion with your physiotherapist (and surgeon) to determine the best outcome for you. There is no absolute right or wrong decision, and so many variables to take into account such as level and type of sport, professional or amateur, occupation, age, other damaged structures in the knee, your ability to commit to a good rehabilitation for the length of time required and the list goes on.
As a general rule, the younger a person is, and the longer career of higher level, intensive rotational sport they have ahead, the more a reconstruction will probably be considered. The best candidates to potentially be able to avoid a reconstruction seem to be:
– Females
– Older age (> 32yo)
– Performing well on our clinical testing especially single leg hop test.

It is interesting to note that in Scandinavia there is a 3 month compulsory prehab period that must be completed before a patient can be considered for a reconstruction, and their results are showing only approximately 50% of patients proceeding to ACLR, whereas the Australian rate sits at around 90%! Perhaps the 3 month pre-operative strength program is a significant factor in returning people to high levels of function without the need for ACLR? Either way, the patient wins – an intensive 3 month prehab strength program may result in avoidance of reconstructive surgery, or it will certainly benefit the post-operative recovery if a reconstruction is chosen.

How do I reduce my risk of re-injury after an ACLR?

In a nutshell:
1. Do a good progressive rehab program that is based on you meeting specific testing criteria, not one that is based on you progressing or returning to activity simply because of time frames. There are many studies to support this, with one in particular showing that 38% of athletes who DID NOT meet discharge criteria, sustained a second ACL on return to sport; whereas only 5% of athletes who DID meet all discharge criteria went on to sustain a second ACL injury.
2. Do your rehabilitation for a minimum 6 months. Most people are pretty good for the first 3-4 months of then rehab, but then drop away. A 6 month rehab program results in a greater chance of all discharge criteria being successfully met, and therefore less risk of re-injury!
So there you go…and there’s more to come! In the final instalment, we will look at the preventative programs that are successfully being used before training and games as part of the standard warm up session, and finally – a bit about how kangaroos may be the great news we are looking for in the fight against ACL recurrences!

Anthony Lance
SSPC Physiotherapist

References: available on request