When it comes to elite sports and sports medicine, a balance needs to be found between getting players back as quickly as possible while doing so in a manner that doesn’t disproportionately increase risk of another injury or other downstream impacts.
There’s arguably no greater example in football than players returning from anterior cruciate ligament (ACL) reconstruction surgery – a major injury to the knee’s most in-demand, stabilising ligament – with nearly a quarter of players under 25 suffering another ACL injury (in either the repaired knee or the other knee).
Any ACL injury comes with an extended return timeline and even longer period to return to performance due to both physical and mental deficits. My benchmark is typically 18 months post-surgery and the second season following the rupture. A second injury only adds to those effects.
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However, as surgical, physio, and fitness techniques have advanced, there’s been constant pressure to lessen the time off when returning from ACL surgery, with “expedited protocols” becoming more and more widely used.
But, as is always the case with new protocols, it takes time and research to determine the risk/reward, in particular the risks of another injury.
Two of the current key factors for returning to sport are determined through muscle function testing. These are specifically of the quadriceps and hamstrings muscle groups, which are measured using strength-testing instruments (such as the Biodex system) and batteries of strength tests, including isolated hamstring and quadriceps exercises (such as knee extension and knee flexion) and single-leg hop testing.
In accordance with that, a study from the Journal of Orthopedic Sports and Physical Therapy examined if there was any relationship between rates of another ACL injury for athletes younger than 30 and key variables that included symmetrical quadriceps strength, symmetrical muscle function, and overall time to return.
The researchers used a database from “Project ACL” to identify patients who were aged between 15 and 30, and were involved in high knee-demand sports (football being one of those sports) prior to the injury and sustained another ACL injury, confirmed by a medical provider.
Data from Project ACL was used for both the symmetrical muscle function and symmetrical quadriceps strength factor, as each athlete involved completed standardised testing including two strength tests, testing quadriceps and hamstring strength, and three single-leg hop tests.
Following exclusion of subjects for different reasons, for example, not performing the muscle function tests in a time period considered close to his or her time of returning to sport, total of 159 subjects were analysed.
Of these 159 subjects, the average age was 21.5 years (standard deviation of roughly four years) with an average return to sport of 11 months, but 64% returning between seven and 11 months. On average, the athletes undertook the battery of muscle function tests a little over two months prior to returning to sport.
The researchers then performed a statistical analysis to see if any of the variables were significantly associated with an increase in risk for another ACL injury, and the results were quite interesting.
Even though only 24% of the athletes had symmetrical muscle function prior to returning to highly strenuous knee-demanding sports, the analysis found no relationship between either symmetrical quadriceps strength or symmetrical muscle function and prevalence of another ACL injury in either the previously injured or non-injured leg.
However, return time did have a significant relationship with that risk. Athletes who returned to high knee demand sports in less than nine months had nearly a SEVEN TIMES higher risk (!) for a new ACL injury compared to those athletes who returned at nine months or later after surgery. Nearly 67% of the athletes who returned in less than nine months and suffered another injury did so between months eight and nine following the reconstruction.
This study is one of the first to explore how expedited protocols may be impacting new ACL injury rates and it looks like that nine-month mark may be the key inflection for reducing risk for footballers under 25 who are coming off an ACL reconstruction. Roma starlet Nicolo Zaniolo comes to mind, having returned in less than six months before suffering an ACL rupture in his other knee within three months (and that includes time off over pre-season).
Although the muscle strength and function tests didn’t show an association with another ACL injury, there’s still plenty of evidence to show how they do impact fitness and how proper strength and conditioning reduce injury risk overall.
There’s a constant push in the professional sports world to get players back quicker but sometimes we have to take a step back and really assess the risk/reward and how that initial rush may actually lead to more time out over the long-haul. Papers like this one help establish that risk.
Dr. Rajpal Brar, DPT, (@3cbperformance) is a physiotherapist, movement expert, fitness trainer, sports scientist and mindfulness coach. He runs the LA and online based physiotherapy and athletic performance clinic 3CB Performance, and you can subscribe to his Youtube channel (which posts analyses of Lionel Messi and more).