August 2011

Upshots of ankle bracing

In the moment: O&P

Proximal effects could put knees at risk

By Jordana Bieze Foster

Bracing the ankle has kinetic effects at the more proximal joints that could increase the risk of anterior cruciate ligament injury, according to research from Iowa State University presented in August at the annual meeting of the American Society of Biomechanics in Long Beach, CA.

Investigators analyzed 10 healthy volunteers (eight women) as they performed forward and backward horizontal jumps onto a force platform from a 45° angle, landing each jump on one foot. Participants were tested while unbraced and while wearing a rigid stirrup-style ankle brace—the same brace worn prophylactically by all members of the university’s women’s volleyball team at that time.

They found that loading rates for knee extension and knee varus were significantly higher during the braced condition than the unbraced condition, which may suggest an increased risk of knee injury, according to Elizabeth “Kate” Stafford, MPT, a doctoral student in the Department of Kinesiology at Iowa State, who presented her findings at the ASB meeting.

“Loading rate is a measure of how quickly the tissue has to take up the force of landing,” Stafford said. “A faster loading rate usually is not as good, because it means the tissues have less time to adapt to the load. They’re having to stabilize much more quickly when they’re wearing the brace.”

Despite the increased loading rates, the researchers did not observe any increase in joint moments at the knee for the braced condition compared to the unbraced condition. However, they did find that bracing was associated with a significant increase in hip adduction moment.

“We expected to see an increase in knee frontal plane moments because the knee is the next most proximal joint from the ankle,” Stafford said. “But when you think about it, the muscles that control knee abduction and adduction are largely at the hip.”

Although differences between braced and unbraced conditions were not related to jump direction, the researchers were intrigued to find that backward jumps were significantly more likely to result in increased varus and valgus moments at the knee and increased adduction moments at the hip.

An elevated knee valgus moment has been cited by previous studies as a risk factor for ACL injury, but that particular kinetic effect has not been reported in previous studies of the effect of ankle bracing on landing biomechanics. A 2006 study from Indiana University published in the Journal of Athletic Training found that wearing a rigid stirrup-type brace during a drop landing was associated with significant increases in internal-external rotation torque at the knee but not in varus-valgus torque.

In a 2010 study published in the Journal of Sport Rehabilitation, researchers from the University of North Carolina at Charlotte found that knee joint angular displacement during a drop landing was significantly reduced while wearing a semirigid ankle brace compared to an unbraced condition, but that hip angular displacement was not significantly affected. That study also found that bracing was associated with significantly faster time to peak vertical ground reaction force than no bracing.

The Iowa State researchers chose to study horizontal, angled, forward and backward jumps instead of drop landings to more closely mimic the type of athletic situation in which noncontact ACL injuries often occur.

“Rarely are we straight-plane in sports,” Stafford said. “That’s why we did the jumps at a 45° angle and in forward and backward directions, to try to replicate that unpredictability.”

The next step for Stafford and colleagues is to repeat the study and compare the effects of bracing in participants who are unaccustomed to brace wear (like those in the current study) to the effects in habitual brace users (in this case, the Hawkeye women’s volleyball team).

2 Responses to Upshots of ankle bracing

  1. Excellent point! Being a podiatric consultant for Sports Performance Volleyball, one of the countries leading clubs here in Ill., I’ve seen hundreds of kids who have used routinely ankle braces ( typically Active Ankle) over decades because it was usually “required routinely”. I’ve ALWAYS been concerned about creating problems above, including “routine”ankle tape for any of these athletes in all sports. Quite commonly, if the athlete had ANKLE PROBLEMS, then tape or brace made sense- although my goal was to put these athletes into custom orthotics for their best functional positioning, aggressively strengthen their feet & ankles & THEN individually determine if any tape or brace was productive. Think about it- brace or tape tight cavus foot type & then do the same for hyper mobile pronated foot? By the way, I’ve seen easy combination with the orthotics & ankle bracing when indicated make huge improvements in some of the persistant knee overuse symptoms like jumpers knee & other knee tendinitis problems. Restrict or inhibit needed ROM in foot-ankle– possible consequences above….Great article!

  2. R.J. Clifton, MS, ATC, LAT, CKTP says:

    When reviewing this study, there are many things that need serious attention before any conclusions are drawn. To begin, the sample size is very small. And, of the 10 people in this study 8 were women. With the large percentage of the sample being women, there are several things that should have been addressed. 1) Quad strength/Quad-Hamstring Ratio, 2) How does the Q angle effect knee valgus and knee varus/hip adductionmeasurements upon landing, 3) One foot landing is contray to most ACL Prevention Program on the marrket, Does increased hip adduction play a direct role in knee injuries, 4) How often does an athlete, during competion or live practice, jump backward landing on one leg? 5) Is there statistical significance showing a correlation between internal/external torque at the knee and an increase in knee injuries? 6) The 2010 study from the Journal of Sports Rehabilitation put out by the University of North Carolina found that the angular displacement at the knee was decreased when wearing an ankle brace during a drop landing. They also found no hip displacement of significance. 7) The semi ridgid ankle brace is designed to transmitt ground forces to the lower leg by way of the stirrup. So, how can peak vertical ground reaction force be significantly faster? 8) This study did not look at lateral drop landings at forty-five degrees; if she was truely looking for the replication of unpredictability of sports why not include lateral drop landings? Lateral movement is very common in sports. 9) As for her comment on repeating the study with people unaccustomed to brace wear, there has to be a level of neuromuscular pattern learning in these people and that would have to effect, maybe even scew the data collected. 10) What surface and what kind 0f footware was worn? These are important/relavant to this study because semi-ridgid ankle braces must be worn with a shoe to be effective. The surface in most, but not all, athletic endevors is rarely perfectly flat and they vary from sport to sport(i.e. baseball outfield or the basketball court).

    In conclusion, ultimantly this study and the podiatrist’s comments need to be taken with a gain of salt. You also have to keep in mind that the podiatrist likes custom orthotics because he can bill more for those than he can for an Active Ankle. And, you can not tell me that the doctor is not influenced by the potential difference in income, so his comments are more than likely scewed. Personally in more than twenty years of practice, including the use of the Active Ankle, I have yet to see an ACL tear while the athlete was wearing Active Ankles. Remember, when reading new research you don’t want to throw the baby out with bath water.

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