Measuring the 4 Components of Athlete Knee Health

Photo: Chris Williams
Athlete: Kayli Farmer

Knee pain in male and female athletes is a common complaint across many sports. It’s one of the joints that works hardest in many settings as athletes accelerate, decelerate, and change direction.

We hear about ACL injuries a lot, especially in relation to sports like soccer, volleyball, or basketball. 1,2,3 Female athletes are 2-8x more likely to suffer from an ACL injury than their male peers. 4 But while we hear about ACL injuries most often, it's good to keep in mind that knee injuries encompass a lot more than just that.

These injuries are often non-contact… and seem to come out nowhere. Other times, it’s pain that athletes have ignored or tried to push through for too long, and the body finally says “enough.” We try to teach our athletes that pushing through pain doesn’t get you an award. It gets you hurt.

“You play stupid games; you win stupid prizes,” as kids these days say. Some of our athlete still play stupid games, despite our best advice. Recovery is an athlete’s best weapon in these situations.

So what can we do as strength and conditioning coaches to try and evaluate our athletes’ knee health? We’ve always kept an eye on movement quality and placed emphasis on the right strength training to minimize knee injury risk. That won’t be changing.

Now, we’re introducing a new step. We’re better monitoring health through consistent measurement to identify potential issues overtime.

The 4 Muscle Groups Essential to Knee Health

Assuming the athlete is a good mover, has good core stability, and demonstrates good motor control, monitoring these four muscle groups might give us some better, more individualized insights on each athlete’s knee health.

The four direct muscle groups that help stabilize the knee:

  1. Hamstrings

  2. Quadriceps

  3. Hip Flexors

  4. Hip External Rotators

Think of these muscle groups like a chain. A chain is only as strong as it’s weakest link, so each muscle group is important. These are going to be working in tandem to keep the knee stable and distribute and absorb forces away from the knee.

As strength and conditioning coaches, we’ve long provided training programs that benefit long-term knee health. Many of movements that we program check all the boxes for each of these groups, as well as core stability and good motor control.

However, we were not specifically measuring the strength of these muscle groups… until now. Recent studies have demonstrated an association in the strength of these muscle groups compared to quantifiable reductions in the risk of knee injury in female athletes.5

And the reverse may be true— weakness in these areas might help us identify potential risk to the knee.

Knee health is impacted by more than just these four muscle groups, but these data points on muscle groups give strength and conditioning professionals additional lenses on their injury reduction programs. While we can’t 100% prevent knee injuries, we can all work towards minimizing their occurrence!

Muscle Group Benchmark Tests

The only way to know that strength is progressing is to test, train, and retest. All of our athletes’ test measurements will be logged in the CoachMePlus app where we can track their progress.

Each test uses readily accessible, inexpensive equipment that can all be purchase for just over $100 total. We’re rolling these tests out to our athletes at the end of March.

Hamstring Test

Rationale: An increase (1 standard deviation) in hamstring strength has been "associated with a 35% decreased risk for overuse knee injuries." 5

We’ve long emphasized the hamstring training since many of our athletes have been quad-dominant. This isometric test gives us a clear indicator progression of strength (or weakness) over time.

Equipment needed:

We measure strength as a function of force. The athlete lies on the floor on their stomach with the ankle cuff tied around their ankle and their leg positioned at 90˚. That cuff is attached to the heavy duty hanging scale, which is secured to rack. The athlete contracts their hamstring and pulls forward with their ankle while the coach stabilizes the hanging scale. The coach records the highest reading in pounds.

Quadriceps Test

Rationale: An increase (1 standard deviation) in quadriceps strength has been "associated with a 30% decreased risk for overuse knee injuries." 5

Equipment needed:

We measure strength as a function of force. The athlete sits in a chair with the ankle cuff tied around their ankle. That cuff is attached to the heavy duty hanging scale, which is secured to a rack. The athlete lifts their unencumbered foot off the floor to minimize interference with the other leg’s measurement. They then contract their quadriceps and pulls forward with their ankle while the coach stabilizes the hanging scale. The coach records the highest reading in pounds.

Hip Flexors Test

Rationale: An increase (1 standard deviation) in hip flexor strength has been "associated with a 28% decreased risk for overuse knee injuries." 5

Equipment Needed:

  • 10 pound kettlebell (≈$25)

We record strength as a function of time (duration). The athlete places their foot through the handle of the kettlebell and holds their leg at 90˚ from their hip. The athlete holds this position for as long as they can. We time their attempts with a stopwatch and record the results.

Hip External Rotators: Augustsson Strength Test

Rationale: An increase (1 standard deviation) in quadriceps strength has been "associated with a 35% decreased risk for overuse knee injuries." 5

This test was developed by Dr. Jesper Augustsson in 2016. He created a highly reliable test with a custom device built out of readily available materials.6 We were able to purchase the components we needed to build our own for less than $50, and some sewing help from my mother-in-law. (Thanks, Shellie!)

Equipment needed:

In this test, we measure strength as a function of peak distance. The athlete lays on one side, and the device is placed around their legs a few inches above their knee. We record the starting measurement on the tape. The athlete then opens up their hips, and we record the ending measurement. Then, we subtract for the difference, and record that as the final measurement in CoachMePlus.

Device Components

Another angle on how it is put together

Next Steps

As we gather this testing data, we’ll start identifying trends. If other S&C coaches, performance coaches, or sport scientists want to participate, we will gladly share our anonymized data to advance the study of knee health forward. We hope to validate this methodology with a local university so that others outside of us can compare numbers and start to standardize what “good” is for athletes.

We’ll use the results of these tests to inform our injury reduction programming for athletes on an individual level. We’ll continue to focus on improving core strength, balance, and agility, and progress the athletes from body weight to weighted movement… because better movers means better (and safer) athletes.

Interested in training with us?

We build athletes. We offer in person training at our facility in Indianapolis as well as online training across the nation.

References

  1. Cullen, M. (n.d.). Why female soccer players are at higher risk of ACL injuries: Wentworth-Douglass Hospital. Why Female Soccer Players Are at Higher Risk of ACL Injuries | Wentworth-Douglass Hospital. Retrieved January 27, 2023, from https://www.wdhospital.org/wdh/services-and-specialties/orthopedic-care/blog/why-female-soccer-players-are-at-risk-of-acl-injuries

  2. Giza E, Mithöfer K, Farrell L, et al (2005). Injuries in women’s professional soccer. British Journal of Sports Medicine 2005;39:212-216.

  3. Iwatsu, J., Yabe, Y., Sekiguchi, T., Momma, H., Tsuchiya, M., Kanazawa, K., Yoshida, S., Sogi, Y., Nagatomi, R., & Hagiwara, Y. (2023). Knee pain in young sports players aged 6-15 years: a cross-sectional study in Japan. BMC sports science, medicine & rehabilitation, 15(1), 16. https://doi.org/10.1186/s13102-022-00606-y

  4. MacMillan, C. (2020, February 14). Are ACL tears really more common in women? Yale Medicine. Retrieved January 27, 2023, from https://www.yalemedicine.org/news/sports-injuries-gender

  5. O'Kane, J. W., Neradilek, M., Polissar, N., Sabado, L., Tencer, A., & Schiff, M. A. (2017). Risk Factors for Lower Extremity Overuse Injuries in Female Youth Soccer Players. Orthopaedic journal of sports medicine, 5(10), 2325967117733963. https://doi.org/10.1177/2325967117733963

  6. Augustsson J. (2016). A NEW CLINICAL MUSCLE FUNCTION TEST FOR ASSESSMENT OF HIP EXTERNAL ROTATION STRENGTH: AUGUSTSSON STRENGTH TEST. International journal of sports physical therapy, 11(4), 520–526. https://pubmed.ncbi.nlm.nih.gov/27525176/

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