Why ACL Injuries Are Becoming More Prevalent

Why ACL injuries are becoming more prevalent

ACL injuries are more prevalent in Australia than in most comparable countries, and the numbers have been climbing for years. Zbrojkiewicz and colleagues, writing in the Medical Journal of Australia in 2018, reported that the rate of ACL reconstruction in Australia is the highest in the world and rising, with the sharpest increases in children and adolescents.

That's a big claim, so it's worth pulling apart what sits behind it. Several things are happening at once, and they're not all bad news.

More people are playing, and playing more often

Exposure is the simplest explanation. The more hours you spend cutting, landing and pivoting, the more chances you have to load the knee in the position where the ACL fails. Australia has a large recreational sporting population playing across summer and winter, and plenty of people now play two codes or add a social competition on top of club footy.

Junior athletes are a particular story. Year-round representative programs, academy squads and specialising in one sport before the body has finished growing all stack exposure into the same joint without much of an off-season.

Women's participation has grown quickly

Female participation in sport has expanded enormously since school sport opened up in the 1970s, and again over the past decade with professional and semi-professional pathways in AFLW, NRLW, cricket and football. More athletes playing means more injuries in absolute terms.

The rate matters too. Webster and colleagues (2021) looked at the first three years of AFLW and found roughly one ACL injury per club per season, and that when exposure hours were accounted for, ACL injury was the most frequent injury per 1000 player hours. They reported a rate around six times higher than the men's AFL competition, which already sits among the highest of any sport worldwide.

A gap that size isn't explained by anatomy alone. AFLW players in those early seasons had shorter pre-seasons, fewer contracted hours and less accumulated strength training history than full-time male professionals. Preparation time is one of the few variables in that list that anyone can change.

The games have got faster

Rule changes and competition structures have pushed the physical demands up. The NRL's six-again rule reduced stoppages and increased ball-in-play time. AFL grew from a Victorian competition into a national one, adding travel load on top of match load. More fixtures, more competitions, more flights, less recovery between hard efforts.

Fatigue changes how people move. Landing mechanics, trunk control and the ability to decelerate all degrade late in games and late in seasons, and that's when a lot of non-contact ACL injuries happen.

Gaps in athletic development

No study proves that weak athletic development programs directly cause ACL tears. What exists is a body of work on neuromuscular training, strength and landing mechanics in relation to knee injury rates, and programs built from it such as Prep to Play, developed with the AFL and La Trobe University, and the FIFA 11+ warm-up.

The practical point is about preparation. Plenty of community athletes arrive at round one having done almost no strength work, no plyometrics and no deceleration or change-of-direction practice, then play 20 minutes of high-intensity football on a wet ground. Longer, better-structured pre-seasons and consistent gym exposure give the knee more to work with.

We are also finding more of them

Part of the rise is detection. MRI only became widely available from the 1980s, and Medicare funding that allows bulk-billed MRI for suspected ACL injury referred by a GP is comparatively recent. Scan more knees and you diagnose more ACL tears, including partial injuries that would once have been called a bad sprain.

That doesn't account for the whole trend, but any honest reading of the incidence data has to allow for it.

What an ACL injury actually involves

The anterior cruciate ligament runs diagonally through the middle of the knee and limits the tibia sliding forward on the femur, along with rotation. Most ACL injuries in field and court sports are non-contact: a sudden deceleration, a sidestep, or landing from a jump with the knee collapsing inward and the foot planted.

Common features people describe are a pop or crack, an immediate sense that the knee has shifted, swelling that comes on within a few hours rather than days, and a feeling of the knee giving way when they try to turn. Around half of ACL injuries also involve the meniscus or other structures, which is one reason assessment doesn't stop at the ligament.

What assessment looks like

A first appointment starts with the story: the exact mechanism, whether there was contact, how fast the swelling appeared, whether you could keep playing, and your injury and training history.

The physical examination looks at swelling, range of motion, quadriceps activation and how you weight bear. Ligament tests such as Lachman's, the anterior drawer and the pivot shift assess how the tibia moves relative to the femur, and the knee is also checked for meniscal and collateral ligament involvement. Where the findings suggest an ACL injury, the next step is usually a GP referral for MRI to confirm what's involved before anyone makes decisions about surgery or non-surgical rehabilitation.

What rehabilitation realistically looks like

Both surgical reconstruction and structured non-surgical rehabilitation are used, and the choice depends on the imaging findings, associated injuries, age, knee stability in daily life and what you want to return to.

Either way, rehabilitation is measured in months, not weeks, and published return-to-sport criteria typically involve restoring full range of motion, quadriceps and hamstring strength within a reasonable margin of the other leg, hop and jump testing, and progressive re-exposure to running, cutting and contact. Individual timeframes vary a lot, and criteria-based progressions are generally preferred to calendar dates.

The research on load management, neuromuscular training and return-to-sport testing has moved quickly over the past decade, and there is more coming. If injury reduction work keeps filtering down from professional programs into community sport, the incidence figures are the place it should eventually show up.

If you would like it assessed, you can book a free injury assessment.