ACL injuries in young female athletes: why the risk is higher, and the 20 minutes that halve it

In high-school sport, girls tear their ACL 1.4 times as often as boys — and over four times as often in basketball. A neuromuscular warm-up cuts that risk by roughly 60% in 13-19 year-old athletes, costs twenty minutes twice a week, and almost no team actually does it. The evidence, and what changes on Monday.

The anterior cruciate ligament is the single injury most likely to change a girl's sporting trajectory: months out, surgery in most cases, and a return that is never guaranteed. The part that gets told least is that the risk is neither randomly distributed nor fixed: there is a warm-up with solid evidence behind it that cuts risk by roughly 60% in teenage athletes, costs twenty minutes twice a week, and almost no team actually does it.

In short

  • In high-school sport, girls sustain 1.40 times the ACL injuries of their male peers (95% CI 1.25-1.57); in basketball the ratio rises to 4.14 (Bram et al., 2021).
  • The gap opens with puberty: after the growth spurt girls land with significantly greater knee valgus than boys, whose landing does not change (Ford et al., 2010).
  • Neuromuscular training lowers risk from 1 in 54 to 1 in 111 (OR 0.51); among 13-19 year-olds the effect is stronger (OR 0.38) (Petushek et al., 2019).
  • It only works if it is actually done: above ~66% compliance (Sugimoto et al., 2012). Among German amateur coaches only 32.1% use the FIFA 11+ programme, and just 40.8% of those do it twice a week as prescribed (Wilke et al., 2018).
  • After reconstruction, 23% of under-25s who return to sport sustain a second ACL injury (Wiggins et al., 2016).

Do girls tear their ACL more often than boys?

Yes — and it's worth using the right numbers rather than the ones in circulation. The "2 to 8 times" figure has been repeated for years, but it comes from older estimates and highly selected samples. The reference point for youth sport is different: a systematic review with meta-analysis of high-school athletes reports 0.084 ACL injuries per 1,000 athlete-exposures in girls (95% CI 0.077-0.091) versus 0.060 in boys (95% CI 0.055-0.065) — a rate ratio of 1.40 (95% CI 1.25-1.57) (Bram et al., 2021).

An average, though, hides more than it shows. The same work finds the gap is almost entirely driven by the sport: in basketball girls carry 4.14 times the risk of boys (95% CI 2.98-5.76), while the highest absolute rate of all is in girls' soccer (0.166 per 1,000 exposures). Put usefully for a coach: there is no such thing as "girls' risk" — there is the risk of this girl in this sport, and cutting-and-landing sports are where to start.

Why the gap opens at puberty

Here the common explanation — "it's female anatomy" — is not enough, because the anatomy is there at 8 too, when the gap is not. What changes in between is puberty.

That puberty, though, is not a date: it is a phase with a speed of its own, and the moment the body changes fastest has a name — peak height velocity. That is when levers lengthen and landing changes, and it is the reason the neuromuscular warm-up should not be dropped in exactly the years an athlete grows most.

A longitudinal study of 315 young athletes, retested a year apart, measured how they land from a jump: in the pubertal group girls increased their peak knee abduction (the inward collapse known as dynamic valgus) from one year to the next (p<0.001), while their male peers did not change at all (p=0.90). After puberty the distance is stark: -9.3° in girls versus -3.6° in boys (p<0.001), with abduction moments nearly double (-21.9 Nm vs -13.0 Nm; p=0.017) (Ford et al., 2010).

The physiological reading is the one that runs through nearly every topic on these pages: the body grows faster than neuromuscular control can adapt. It is the same reason pain changes in nature during this phase and why load should follow pubertal stage, not the date on an ID card. With one important difference: here the window of risk is also the window in which training works best.

Can it really be prevented? What the numbers say

Yes, and the evidence is among the strongest in female youth sport. A meta-analysis of 27,231 athletes and 347 ACL injuries estimated that preventive neuromuscular training reduces risk from about 1 in 54 to 1 in 111 (OR 0.51; 95% CI 0.37-0.69) (Petushek et al., 2019).

The detail that matters for youth clubs is in the subgroup. Among athletes aged 13-19 the odds ratio drops to 0.38 (95% CI 0.24-0.60) — roughly 60% less risk — while among college and professional athletes aged 19-24 it stops at 0.65 (95% CI 0.48-0.89). The earlier you start, the more it returns. The exercises with the greatest protective benefit in that same work are landing stabilisation, the Nordic hamstring, lunges and heel-calf raises: nothing that requires equipment or a physiotherapist on site.

How many minutes does it actually take?

The average dose of the programmes that worked is 24.1 minutes per session, 2.51 times a week (Petushek et al., 2019). About twenty minutes, twice a week, in place of the warm-up already being done.

But the decisive variable isn't the content — it's consistency. A meta-analysis of athletes aged 14-22 found that studies with high compliance recorded an ACL injury incidence 0.27 times that of low-compliance studies (95% CI 0.07-0.80), and estimates that overall compliance must exceed 66% for risk to fall meaningfully (Sugimoto et al., 2012). The trial closest to our population confirms it: in a cluster randomised trial of 226 Canadian female footballers aged 13-18, the benefit appeared only in teams with high adherence to the FIFA 11+ programme (IRR 0.28; 95% CI 0.10-0.79) (Steffen et al., 2013).

This is the most important point in the article: a programme done halfway is not half a programme. It risks being no programme at all.

If it works this well, why does almost nobody do it?

Because the obstacle isn't scientific, it's organisational — and that too has been measured. In a survey of 1,223 German amateur coaches, only 42.6% knew the 11+ programme, 32.1% used it, and among users just 40.8% did it twice a week as recommended (Wilke et al., 2018).

To be precise: that sample covers German amateur football, largely male youth and adult teams, so it does not describe Italian women's sport. It doesn't quantify our problem; it shows that even where a programme is famous and free, the distance between "it exists" and "it happens twice a week" is enormous. The recurring barriers are always the same: too little time, too little belief in its effectiveness, nobody keeping count.

Which is exactly why ACL prevention is, at bottom, a question of coaching culture before it is a question of exercises — the same lever that weighs on the words used with athletes and on how many girls stay in a club.

Does the menstrual cycle have anything to do with it?

It's the question that always comes, and it deserves an honest answer rather than a suggestive one. The hormonal hypothesis exists, but the evidence does not currently support it. A systematic review with meta-analysis of 21 studies and 68,758 participants classified the overall quality of evidence as «very low» under GRADE criteria (Herzberg et al., 2017). A later review of neuromuscular and biomechanical risk surrogates concludes the same way: it is not possible to establish which cycle phase carries more risk, and it explicitly urges caution before adjusting preparation and screening on that basis (Dos'Santos et al., 2023).

The practical consequence is clear, and runs opposite to what people expect: there is no basis for adapting load, selection or screening to the cycle phase of a 14-year-old. The cycle should be known, listened to and made speakable — and it is still taboo — but it is not an ACL prevention lever. What is proven to work is neuromuscular training, done in every week of the month.

What happens afterwards, at 15

One figure that should weigh more than it does: after ACL reconstruction, 23% of athletes under 25 who return to sport sustain a second ACL injury — on the same leg or the other one (Wiggins et al., 2016). In the same review the overall rate is 15% (7% ipsilateral, 8% contralateral): young age and a return to high-intensity activity are the two factors that raise it.

Put differently: prevention does not end with the first injury. If anything, the moment neuromuscular work counts most is the return to play — and the decision about when to return belongs to the clinical pathway following the athlete, not to the coach.

Not every painful knee is an ACL

The ACL is the most dramatic knee injury, not the most frequent one. Worth saying, because the attention the ACL has earned — deservedly — has a side effect: it lets the knee that has hurt for months, with nothing ever having happened, go unnoticed.

The difference is in the onset. An ACL rupture has a precise moment: a cut, a landing, a knee giving way. Patellofemoral pain has no start date: it flares on stairs, in squats, in jumps and when sitting for long periods. In the Danish cohort of adolescents with knee pain, 68.3% of cases had an insidious onset, with no trauma at all, and the median duration of pain was 24 months (Rathleff et al., 2013, BMC Musculoskeletal Disorders).

And it is not a minor problem just because it makes no noise: five years later, 40.5% of those adolescents still had pain, and among them 60% had stopped or reduced sport because of the knee (Rathleff et al., 2019, BMJ Open). None of those withdrawals enters an injury statistic.

The practical part: if an athlete says her knee has been hurting "a bit for a while", the useful question is not how much, it is how long — and the answer belongs with a healthcare professional, not with pitch-side management. We covered it at length in the knee that has hurt for months.

What a club can do, starting Monday

None of these is a medical prescription. They are organisational choices within reach of any club:

Where BAB fits

BAB does not train knees and does not diagnose. It does something different and complementary: it helps an athlete recognise her own patterns privately — energy, mood, recovery, perceived load, cycle — and gives the club only aggregated, anonymous signals. On ACL injuries this matters for a precise reason: the factors that make a squad fragile — weeks stacked without recovery, chronically short sleep, load rising in the wrong period — are the same ones that make landing badly more likely when you are tired. The prevention programme is the coach's job. Knowing when the squad is arriving tired at the worst moment is what BAB makes visible, without ever exposing an individual athlete.

Sources

This article is for information only and does not constitute medical advice or a diagnostic tool. A prevention programme does not eliminate injury risk. In case of knee pain, giving way, or after a trauma, consult a sports physician or orthopaedic specialist: the decision about return to activity belongs to the clinicians treating the athlete.

Do girls tear their ACL more often than boys?

Yes, and in youth sport the gap has been measured. A systematic review with meta-analysis of high-school athletes reports 0.084 ACL injuries per 1,000 athlete-exposures in girls versus 0.060 in boys — a rate ratio of 1.40 (95% CI 1.25-1.57). But the gap varies enormously by sport: in basketball girls carry 4.14 times the risk of their male peers (95% CI 2.98-5.76), while the highest absolute rate of all is in girls' soccer, at 0.166 per 1,000 exposures (Bram et al., 2021). Figures like «2 to 8 times» circulate widely: they come from older, more fragile estimates and do not describe the average of school sport.

Can ACL injuries actually be prevented?

Not eliminated, but substantially reduced — and this is one of the strongest bodies of evidence in youth sports medicine. A meta-analysis of 27,231 female athletes and 347 ACL injuries estimated that preventive neuromuscular training lowers risk from about 1 in 54 to 1 in 111 (OR 0.51; 95% CI 0.37-0.69). The effect is strongest in the youngest group: among athletes aged 13-19 the odds ratio drops to 0.38 (95% CI 0.24-0.60), roughly 60% less risk, versus 0.65 among college and professional athletes aged 19-24 (Petushek et al., 2019). It isn't a treatment: it's a warm-up done properly.

How often does it have to be done to work?

The average dose across programmes that worked is about 24 minutes per session, 2.5 times a week (Petushek et al., 2019). And consistency is not a detail: a meta-analysis of athletes aged 14-22 found that studies with high compliance had an ACL injury incidence 0.27 times that of studies with low compliance (95% CI 0.07-0.80), pointing to an overall compliance threshold around 66% (Sugimoto et al., 2012). In the randomised trial closest to our population — 226 Canadian female footballers aged 13-18 — only the teams with high adherence to the FIFA 11+ programme showed reduced injury risk (IRR 0.28; 95% CI 0.10-0.79) (Steffen et al., 2013). A programme done halfway is not half a programme: it risks being no programme at all.

How do you tell an ACL rupture from knee pain that has lasted for months?

By the onset, before the symptoms. An ACL rupture is a single event: there is a precise moment, often a cut or a landing, a knee giving way and in many cases rapid swelling. Patellofemoral pain has no start date: it flares on stairs, in squats, in jumps and when sitting for long periods, and in the Danish cohort 68.3% of adolescent knee pain had exactly that insidious onset, with no trauma (Rathleff et al., 2013, doi:10.1186/1471-2474-14-225). This is not an academic distinction: the second picture is ignored far more often, and five years on 40.5% of adolescents with knee pain still have it, with 60% of those having stopped or cut back on sport (Rathleff et al., 2019, doi:10.1136/bmjopen-2018-024113). In both cases assessment belongs with a healthcare professional.

At what age should preventive neuromuscular warm-ups start?

Early, and before the growth spurt if possible. In the meta-analysis of 27,231 female athletes the protective effect is strongest in the youngest band: among 13-19 year-olds the odds ratio is 0.38 (95% CI 0.24-0.60), roughly 60% less risk, versus 0.65 in athletes aged 19-24 (Petushek et al., 2019). The physiological reason is that the biomechanical gap opens with puberty: after peak growth, girls land with significantly greater dynamic knee valgus than male peers (-9.3° versus -3.6°; p<0.001), while in boys the value does not change over the years (Ford et al., 2010). The window in which risk rises is the same one in which training pays off most: waiting for the senior squad means losing the age at which the programme works best.

Does the menstrual cycle increase ACL injury risk?

The hypothesis exists; the evidence does not currently support it. A systematic review with meta-analysis of 21 studies and 68,758 participants rated the overall quality of evidence «very low» under GRADE criteria — meaning very little confidence in the effect estimate (Herzberg et al., 2017). A later review of neuromuscular and biomechanical risk surrogates reaches the same conclusion: it is not possible to say which cycle phase carries more risk, and the quality of evidence is low to very low (Dos'Santos et al., 2023). The practical consequence is clear: there is no basis for adjusting training, selection or screening around the cycle phase of a 14-year-old. What is proven to work is neuromuscular training, done every week of the month.