Rethinking knee injuries in female athletes

A growing and unacceptable disparity between male and female athletes—worldwide—is the disproportionately higher numbers of serious knee injuries suffered by female athletes relative to males. The only good news associated with this reality has been the extraordinary progress made in orthopaedic surgery in repairing damaged knees. New techniques, tools and procedures represent genuine improvements in the way we respond to ruptured ACL’s. But why, from a coaching standpoint, have we failed so completely to match the progress in repairing injured knees with similar progress in preventing injuries from happening in the first place?

Diagnosing the problem

Current injury rates are telling us that female athletes are poorly prepared for the physical demands of their respective sports and that we must radically change our approach from passively accepting knee injuries to actively preventing them. What is needed is a shift: away from traditional, weight-room based, barbell-dominant, ideas of strength-training and toward a paradigm of dynamic plyometric and running-based training modalities.

The 2023 FIFA Women’s World Cup illuminated—yet, again—the magnitude of the knee injury problem with female field and court sport athletes, specifically with regard to anterior cruciate ligament (ACL) tears. A host of top players did not feature in the tournament due to ACL injuries. At least eighty-eight players from eight of the world’s top women’s football leagues have torn their ACLs since 2021. Similarly, torn ACL’s in the English Women’s Super League and in US NCAA Women’s Soccer are shockingly high and trending upward.

Australia has the dubious distinction of leading the world in ACL injuries. Based on estimations, the annual number of ACL tears in Australia is expected to more than double by 2030-2031 compared to 2017-2018 levels. The women’s format of Australian rules football (AFLW) statistically leads the world in ACL tears when compared to other team sports. The ACL injury rate in the AFLW is three to seven times higher when compared to other female team sports and ten to nineteen times higher when compared to male team sports, such as European handball and football (soccer).

Of course, there is also a financial burden associated with ACL tears. In what is believed to be the first estimate of the financial burden of ACL reconstructive surgery in Australia, Ross, et. al. (2023) derived an individual direct and indirect cost of A$34,079. It is likely this is an underestimation with the study’s inclusions for direct and indirect costs being limited by reported costs in the broader literature. This pioneering study also predicts a 52.9% reduction of ACL injuries and related costs by athletes using injury-reduction program strategies. Significantly: Most of the prevention programs described in the meta-analyses include a mixture of plyometric, strengthening and neuromuscular drills aimed at addressing landing technique and common deficits associated with ACL injuries.

High injury numbers for female athletes are predicated and sustained by a host of unwarranted assumptions. Among these are two contradictory ideas: the first relates to the fundamental nature of males and females, and the second is the approach we take in preparing each for physical challenges.

ACL tears in female athletes are, generally, blamed on female athletes. There is a pervasive acceptance of knee injuries as “something that happens to women.” The conventional thinking goes: Females are developmentally, physiologically and emotionally different from men; these differences put female athletes at a disadvantage; therefore, they are going to be injured—more often and more severely—than their male counterparts. This—conveniently—allows us to blame torn ACL’s on nature—the non-modifiable differences between genders—and avoid considering the possibility that nurture (marginalized, minimalized physical education combined with ineffective coaching and training paradigms) plays a significant part in generating the injury statistics we see, today. Effectively, we are blaming the victims.

Ironically, even as we point to female-male differences as the reasons for disproportionate rates of injury, we generally train males and females as if they were the same. We employ the same methods, venues, and tools for both genders. This is intellectually disingenuous. Females are getting hurt far more often than males. How can we, on the one hand, point to gender differences as causal factors in these injuries, and then fail to address them with female-specific physical preparation?

Female athletes are different from male athletes, but they are not deficient.

There is ample evidence demonstrating that gender-appropriate, physically dynamic training approaches that adequately address joint and tendon vulnerability can significantly and consistently reduce ACL injuries in females to a point where they are statistically comparable to the injury rates for males. What is required is a full, critical-thought re-evaluation of training—training ideas, training venues, training tools and—especially—training priorities.

The focus must change from traditional, quantity-based strength-training using barbells with an out-sized emphasis on maximum strength development to quality-based movement training with the emphasis on running mechanics (acceleration, deceleration, re-direction and re-acceleration). This is no simple challenge to meet, because so many coaches rely on easily quantifiable measures of training evaluation (“How much can she lift?”) and are neither comfortable nor qualified to assess movement patterns subjectively (“How well does she move?”).

Strength remains the essential underpinning of a movement-based training paradigm, but it must be strength that supports and enhances a body’s ability to create, store and express elastic energy utilizing the full spectrum of high-speed force development and eccentric force acceptance. It is a part of the complex, collective whole we call “athleticism,” but strength will always be an irrelevant quantity unless and until it is connected to the athletic qualities that ultimately define an athlete’s chances of competitive success and durability. These qualities and related techniques include:

  • Acceleration
  • Deceleration
  • Linear speed
  • Multi-directional speed
  • Agility
  • Balance
  • Coordination
  • Athletic reaction-response
  • Sport-specific reaction
  • Joint strength and stability
  • Suppleness
  • Power
  • Sport-specific skills

Since the strength we use in sport (and life) will always reflect the means by which it was created, training to survive dynamic, high-speed physical demands by doing repetitive, slow, controlled, resisted movements (almost always done in a single plane) represents a clear contradiction of functional purposes. (You cannot train like a plow-horse and expect to perform like a cheetah.)

The table below illustrates the essential disconnect between what happens in weight-rooms and what happens in competition:

The first critical differential to note is the amount of time required for traditional, external-resistance strength training movements and the far shorter time requirements for multi-directional stopping, starting, and sprinting with sport-specific skills. This explains why simply creating more strength has not resulted in fewer injuries. And then there is the limited (limiting) nature of barbell-resisted movements. Adaptability at competitive speeds requires a far more extensive movement vocabulary than barbells permit. Barbells tell bodies what they can do. Elevating performance while avoiding injury requires tools that ask bodies what they can do.

The training paradigm we propose for creating robust, resiliency in female athletes is one rich in plyometric movements done in conjunction with coordination and reactive demands. There is a common misperception that plyometrics are a high-risk training modality; but evidence shows that plyometric movements actually prevent injuries. The mistaken notion that jumping, hopping, bounding and directional changes are inherently dangerous almost certainly comes from an inability on the part of coaches to create athlete-appropriate progressions. Undoubtably, it is possible to over-match an athlete with a plyometric movement that could result in injury; but this is an example of a coaching failure rather than a reason to avoid plyometrics. It is almost certain that the mistaken belief that plyometrics cause injury has certainly resulted in many field and court sport athletes being insufficiently challenged and prepared.

Research shows that eccentric rate of force development (RFD) distinguishes elite v sub-elite athletes in speed and power sports and events. It is also the most important athletic quality for preventing impact injuries—particularly in women, and frequently cited as a dividing-line between men and women when speed (and gravity) take effect in sprint events. Interestingly, when women are prepared appropriately, they can be competitive with men in events where explosive, mass-specific strength matters as in the initial 10m to 20m of a 100-meter sprint. This shows that eccentric RFD is a trainable quality in women, but it must be programmed consistently, adequately, and year-round.

Moving down the strength spectrum

The values from the table above tell us that weight-room based strength programs are generally focused on the wrong numbers. It isn’t safe or likely that an athlete can be expected to lift anything like two to three times her bodyweight; but dynamic, plyometric training can prepare her to manage and accommodate forces that are even greater, and do so at speed—with stops, re-starts and directional changes—while executing sport-specific skills.

The potential benefits of changing the training paradigm for women are numerous and profound, and they come with no down-sides. A well designed, progressive plyometric-focused program permits athletes to train to play where they play: on the field or court. The tools required are minimal, and a fraction of the cost of a weight-room equipped and sized to train a full team at once. And making the connection between what the athletes do in training to what they do in competition—the “transferability factor”—is easy.

An additional—and critical—reason for considering a training paradigm shift to a female focused training model is the combined psychological and emotional benefit it offers the athletes. Both girls and women are often reluctant to embrace training modes that male athletes enthusiastically use to make themselves bigger. Females are not offered the same social affirmation for muscular hypertrophy as are males. And though it is true that, since most females lack the same levels of testosterone as their male counterparts and, therefore, it is unlikely they could match them in this area, the perception—and concern—that “lifting weights = building bulk” is enough to create reluctance on the part of females and mistrust of coaches who push the weight-room training model.

Making the default training venue a field, court or hillside is less confusing and angst-producing. Posing progressive movement-puzzles for athletes to solve makes training compelling and fun, and results in bodies far more adaptable than adapted. And we should think of adaptability as a highly desirable athletic attribute; the summation of physical qualities resulting in enhanced performance and reduced risk of injury.

Running is the elemental physical element for field and court sport athletes. Good neural patterns associated with running are more easily built-in than retroactively added. As such, optimal running form should be introduced, taught, nurtured, developed and encouraged from an athlete’s youth throughout her career.

Teaching running technique to developmental field and court sport athletes should be an obvious training priority; however, this is often not the case. Athletes are told how fast, how far, which way, but they are rarely taught how to accelerate, decelerate and reaccelerate. There are reasons for this, often including a knowledge gap on the part of the coach, and just as often, the necessary attention to detail and the time required often puts coaches off. Consequently, mediocrity is routinely accepted with many young athletes continuing to run with poor technique, and insufficient skill in stopping and stepping.

A paradigm shift from quantitative performance measures to one focused on mastery of running, jumping, bounding, hopping, landing, stepping and stopping, will require that performance coaches for field and court sports have a well-developed skill set and the knowledge and tools to recognize and improve these athletic qualities. This skill-set begins with a well-trained eye. You cannot train people to move better if you don’t truly know what “better” looks like.

And don’t go . . . if you can’t stop. Optimal braking performance and risk mitigation requires concurrent hip-hinge and knee flexion when decelerating. Additionally, the quality and frequency of steps relating to early deceleration is also essential. With all forms of running, there is an inverse relationship between step-length and frequency. Increasing step length to generate horizontal force production is desirable while accelerating. Deceleration is the mirror opposite whereby, increasing frequency being the best way to accept ground reaction forces and provide self-protection. Deceleration skill combines reactive control of the centre-of-mass (lowering) to keep the weight balanced, not simply extending the heels forward to provide straight-leg braking. Initially negotiating the ground with the heel, impairs the ability to automatically modulate step frequency, greatly diminishing this self-protection. High-speed stepping is a separate, but related skill that is about redirecting ground reaction forces. It requires whole body coordination for both performance and risk mitigation.

Final thoughts

All stakeholders in the athletic development process (athletes, parents, coaches and sports medicine providers) must understand that a torn anterior cruciate ligament is a knee-injury for life. It almost certainly means the end of an athlete’s season, and can mean the end of an athlete’s career. It will almost always mean the diminution of performance. And the knock-on effects from the initial damage—regardless of the surgeon’s skill and the success of the surgical repair—will include progressive, degenerative changes in the affected joint. A knee injury in a young girl will mean increasing discomfort and pain as she ages. This means a gradual decline in her movement options and often leads to struggles in avoiding unwelcome weight-gain (with the attendant negative self-image baggage this often entails). It also means she may need knee-replacement surgery while she is still in the prime years of her life.

The real shame of the ACL epidemic is the reality that so many girls and women could be spared this trauma-spectrum. So many of these injuries can be prevented. Accomplishing this will require much diligence on the part of coaches in critically re-considering their current methods and learning how to see athletic movement—differently, and better—and recognize that only uninjured athletes can take the field and have a chance to reach their athletic potential. Failure to adopt better preparation protocols will doom many more female athletes to unnecessary pain, suffering and financial burden. It should—and will—be recognized as an unforgivable betrayal of trust.