There has been an epidemic of sorts in the past few years regarding ACL  injuries and young female athletes. In fact, 50,000 ACL surgeries were  performed in the United States in 1982, with the majority of ACL  injuries being the non-contact variety; essentially, no direct contact  led to the injury itself. That statistic goes right to the heart of my  concerns with young athletes. If the majority of ACL injuries are  non-contact based, than they are either a result of biological or  mechanical issues to blame. That is, either the injuries are due to  unfortunate, yet genetic structural dysfunctions or the result of  improper loading and mechanical faults which is a matter of poor  coaching.

Here is the fact; women have higher incidences of non-contact ACL  injuries within the context of sporting events than do men. In fact,  according to a  study on this topic recent reports from the National  Collegiate Athletic Association institute that female collegiate soccer  and basketball players were three to four times more likely to have  non-contact injuries than their male counterparts.  There simply has to be an answer accounting for why this is.

In separate studies, several factual elements of ACL injuries were shown:

      1. Non-contact ACL injuries often occur with the knee at modest flexion  along with a valgus motion.2. Quadriceps contraction applies an anterior shear force on the tibia.

3. The above mentioned quadriceps contraction can cause an ACL injury  if the knee flexion angle is less than 30 degrees and the hamstring  musculature does not supply necessary posterior shear force (when  functioning well, the hamstrings provide a counter force which pulls the  tibia back from any translation forward).

Given these points and knowing that female athletes are more prone to  non-contact ACL injuries, several assumptions can be made:

    1. Young female athletes likely do not show as great a degree of knee  flexion and yet more valgus motion than do young male athletes during  athletic events and/or training.2. Young female athletes likely have stronger anterior thigh dominance  than posterior (i.e. more quadriceps involvement than hamstring involvement) during athletic events or training. This factor, of  course, has influence over the anterior versus posterior shearing  forces.

If these assumptions are true, and in fact basic biological factors  (such as Q-angle) are not entirely to blame for this ACL epidemic, then  does poor coaching play a role, at least to some degree, in the female  ACL injury syndrome? For instance, referring to point #1, non-contact  ACL injuries occur when the knee experiences too modest a degree of  flexion and too much valgus during activities such as running, jumping  and cutting are those not mechanical issues that a qualified coach  should notice and correct.

Here is what one study found when attempting to decipher these concerns  (the findings were based on a observations of running, side-cutting and cross-cutting).

      1. Knee flexion angle for female athletes was lower than that for male  athletes.2. Female athlete's knees were steadily in a valgus direction (in  fact, 11 degrees more valgus than male subjects). This is a definitive  problem. According to one study, the load on the ACL due to even a 5  degree motion towards valgus can increase to as much as 6 times of that  when the knee is lined up properly in the frontal plane.

3. Especially during running and side cutting, female athletes  experienced more dominance of the quadriceps than did male athletes.

4. Especially during running and side cutting, female athletes  experienced less dominance of the hamstrings than did male athletes.

The combination of points #3 & 4 indicate a strong concern. While the  increased quadriceps activation does not necessarily infer an anterior  shear, the combination of an increased quadriceps force coupled with  decreased hamstring activation will most certainly increase the  likelihood of anterior shearing on the tibia through the patella tendon.

The point is that female athletes tend to incur knee motions during  activity that are typical for experiencing non-contact ACL injuries.

Here is where the debate and argument gets heated for me. I have been  an outspoken critic for years on the quick fix, short term training  approach that many trainers and facilities implement with younger  athletes. When you are young and athletic, getting is shape for the  upcoming season, improving your vertical jump in 6-weeks, adding 25  pounds to your bench and being able to run at  MPH on those high speed  treadmills should be distant concerns in contrast to developing  fundamental, multi-joint and systemic strength, learning movement  economy (or the most efficient means of running, changing direction etc) and perfecting safe and biomechanically sound movement patterns.  A study on the jumping & landing techniques in elite women's  volleyball concluded brilliantly that concerning technique, athletes who  regularly perform landings and are exposed to the concurrent large  impact forces should concentrate on performing landings using a toe-heel  contact pattern with greater knee flexion.

What a novel concept! Actually TEACH young athletes the technique of  how to run, jump, land and move BEFORE you program endless numbers of  drills and exercises.

Therein lies the crux of my concern far too many trainers and facilities  make the erroneous error of trying to maximize the ability of a young  athlete as it relates to performance markers (such as vertical jump)  rather than advocating for a developmental approach to improvement that  is founded on fundamentals and basics. In doing so, these trainers are  dampening the potential success a young athlete may achieve down the  road, and compounding the problem of injury potential rather than easing  it.

Here is an example of how you would teach a squat, for example, to a  young female athlete.

Five Step Process

      1. Foot Position. I typically start with feet shoulder width apart and  toes pointing straight ahead. Once the athlete is comfortable with the  exercise, we can explore other comfortable positions.2. Lift In-Step. I don't want this to sound as though I have young  athletes remove their in-steps completely off the ground, but we instill  the notion that they need to be performing the squat exercise by pushing  through the outside portion of their heels. This accomplishes a couple  of things: a) the issue of knee valgus is removed b) Hip, knee and ankle alignment is guaranteed.

3. Set Eyes & Head. When the eyes are down, the head and upper torso  will follow. This causes a forward motion during the eccentric phase  and causes both an anterior force through the knee as well as  misalignment of the cervical, thoracic and lumber spine.

4. Push Hips Back. First time squatters and young athletes who were  poorly guided will often automatically descend into the squat with an  anterior motion (i.e. weight on the toes). By actively pushing the hips  back, we are promoting more hip extension during the concentric phase of  the squat and therefore higher activation of the hamstrings and glutes  with proportionately less quadriceps involvement, consequently reducing  anterior shearing forces at the knee joint.

Some, and in many cases all, of the steps in the preceding sequence can  be used to teach several lower body exercises including single leg  squats, step-ups, lunges and side steps.

One of the most important factors to understand is that squatting, long  considered by many to be an unsafe exercise, is actually a critically  important progressive action that aids in teaching the fundamental  movement patterns associated with preventing ACL injuries.

References:

Jumping & Landing Techniques In Elite Women's Volleyball, Tillman,  Haas, Brunt, Bennett, Journal of Sports Science and Medicine, 04

A Comparison Of Knee Joint Motion Patterns Between Men & Women In  Selected Athletic Tasks, Malinzak, Colby, Kirkendall, Yu, Garrett,  Clinical Biomechanics. 01