Functional Ankle Instability and the Peroneals 


Lots of links available here with today’s blog post. please make sure to take your time and check out each one (underlined below) 

As you remember, the peroneii (3 heads) are on the outside of the lower leg (in a nice, easy to remember order of longus, brevis and tertius, from top to bottom) and help to stabilize the lateral ankle. The peroneus brevis and tertius dorsiflex and evert the foot while the peroneus longus plantarflexes and everts the foot. We discuss the peroneii more in depth here in this post. It then is probably no surprise to you that people with ankle issues, probably have some degree of peroneal dysfunction. Over the years the literature has supported notable peroneal dysfunction following even a single inversion sprain event. 

Functional ankle instability (FAI) is defined as ” the subjective feeling of ankle instability or recurrent, symptomatic ankle sprains (or both) due to proprioceptive and neuromuscular deficits.” 

Arthrogenic muscle inhibition (AMI) is a neurological phenomenon where the muscles crossing a joint become “inhibited”, sometimes due to effusion (swelling) of the joint (as seen here) and that may or may not be the case with the ankle (see here), or it could be due to nociceptive input altering spindle output or possibly higher centers causing the decreased muscle activity. 

This paper (see abstract below) merely exemplifies both the peroneals and FAI as well as AMI.

Take home message?

Keep the peroneals strong with lots of balance work!

The Gait Guys: bringing you the meat, without the filler!                                                                         

Am J Sports Med. 2009 May;37(5):982-8. doi: 10.1177/0363546508330147. Epub 2009 Mar 6.

Peroneal activation deficits in persons with functional ankle instability.

Source

School of Kinesiology, University of Michigan, 401 Washtenaw Avenue, Ann Arbor, MI 48109, USA. riannp@umich.edu

Abstract

BACKGROUND:

Functional ankle instability (FAI) may be prevalent in as many as 40% of patients after acute lateral ankle sprain. Altered afference resulting from damaged mechanoreceptors after an ankle sprain may lead to reflex inhibition of surrounding joint musculature. This activation deficit, referred to as arthrogenic muscle inhibition (AMI), may be the underlying cause of FAI. Incomplete activation could prevent adequate control of the ankle joint, leading to repeated episodes of instability.

HYPOTHESIS:

Arthrogenic muscle inhibition is present in the peroneal musculature of functionally unstable ankles and is related to dynamic peroneal muscle activity.

STUDY DESIGN:

Cross-sectional study; Level of evidence, 3.

METHODS:

Twenty-one (18 female, 3 male) patients with unilateral FAI and 21 (18 female, 3 male) uninjured, matched controls participated in this study. Peroneal maximum H-reflexes and M-waves were recorded bilaterally to establish the presence or absence of AMI, while electromyography (EMG) recorded as patients underwent a sudden ankle inversion perturbation during walking was used to quantify dynamic activation. The H:M ratio and average EMG amplitudes were calculated and used in data analyses. Two-way analyses of variance were used to compare limbs and groups. A regression analysis was conducted to examine the association between the H:M ratio and the EMG amplitudes.

RESULTS:

The FAI patients had larger peroneal H:M ratios in their nonpathological ankle (0.399 +/- 0.185) than in their pathological ankle (0.323 +/- 0.161) (P = .036), while no differences were noted between the ankles of the controls (0.442 +/- 0.176 and 0.425 +/- 0.180). The FAI patients also exhibited lower EMG after inversion perturbation in their pathological ankle (1.7 +/- 1.3) than in their uninjured ankle (EMG, 3.3 +/- 3.1) (P < .001), while no differences between legs were noted for controls (P > .05). No significant relationship was found between the peroneal H:M ratio and peroneal EMG (P > .05).

CONCLUSION:

Arthrogenic muscle inhibition is present in the peroneal musculature of persons with FAI but is not related to dynamic muscle activation as measured by peroneal EMG amplitude. Reversing AMI may not assist in protecting the ankle from further episodes of instability; however dynamic muscle activation (as measured by peroneal EMG amplitude) should be restored to maximize ankle stabilization. Dynamic peroneal activity is impaired in functionally unstable ankles, which may contribute to recurrent joint instability and may leave the ankle vulnerable to injurious loads.

all material (except for the study); copyright 2013 The Gait Guys/ The Homunculus Group. All rights reserved. Please ask before you lift our stuff. If you are nice and give us credit, we will probably let you use it!

Since the world did not end, you should probably think twice about those motion control shoes….

WE can all agree that there is a time and a place for motion control shoes. For people with chronic ankle sprains or lateral instability (ie, an incompetent lateral compartment; peroneus longus, brevis or tertius), it is neither the time, nor the place.

The lateral ankle is stabilized by both static (ligaments: above lower left) and dynamic (muscles above, lower right) elements. This is often called “the lateral stabilizing complex” The lateral ankle (ie the lateral malleolus) also projects more inferiorly than the medial. This means that when push comes to shove, the ankle is more likely to invert (or go medially) than evert (or go laterally). What protects it? The static component consist of three main ligaments (seen above) the posterior and anterior talofibular ligaments and the calcaneofibular ligaments. The dynamic components are the peroneii muscles. These muscles not only stabilize but also exert an eversion (brings the bottom of the foot to the outside) force on the ankle.

So what you say?

according to one study we found “Using an in-shoe plantar pressure system, chronic ankle instability subjects had greater plantar pressures and forces in the lateral foot compared to controls during jogging.”

Hmmm. Remember the midsole? (If not click here and here for a review) Motion control shoes are medially posted. That means they provide more support medially or  have a tendency to tip the foot laterally. SO, motion control shoes shift forces laterally.

A person with chronic ankle instability has weakness of either the static, dynamic, or both components of the lateral stabilizing complex.

bottom line? make sure folks have a competent lateral stabilizing complex and if they don’t, you may want to think twice about using a motion control shoe.

Ivo and Shawn. Increasing your shoe geekiness coefficient on daily basis!                                                                                                                                                    

Foot Ankle Int. 2011 Nov;32(11):1075-80. Increased in-shoe lateral plantar pressures with chronic ankle instability. Schmidt H, Sauer LD, Lee SY, Saliba S, Hertel J. Source University of Virginia, 2270 Ivy Road, Box 800232, Charlottesville, VA 22903, USA.

Abstract BACKGROUND:

Previous plantar pressure research found increased loads and slower loading response on the lateral aspect of the foot during gait with chronic ankle instability compared to healthy controls. The studies had subjects walking barefoot over a pressure mat and results have not been confirmed with an in-shoe plantar pressure system. Our purpose was to report in-shoe plantar pressure measures for chronic ankle instability subjects compared to healthy controls.

METHODS:

Forty-nine subjects volunteered (25 healthy controls, 24 chronic ankle instability) for this case-control study. Subjects jogged continuously on a treadmill at 2.68 m/s (6.0 mph) while three trials of ten consecutive steps were recorded. Peak pressure, time-to-peak pressure, pressure-time integral, maximum force, time-to-maximum force, and force-time integral were assessed in nine regions of the foot with the Pedar-x in-shoe plantar pressure system (Novel, Munich, Germany).

RESULTS:

Chronic ankle instability subjects demonstrated a slower loading response in the lateral rearfoot indicated by a longer time-to-peak pressure (16.5% +/- 10.1, p = 0.001) and time-to-maximum force (16.8% +/- 11.3, p = 0.001) compared to controls (6.5% +/- 3.7 and 6.6% +/- 5.5, respectively). In the lateral midfoot, ankle instability subjects demonstrated significantly greater maximum force (318.8 N +/- 174.5, p = 0.008) and peak pressure (211.4 kPa +/- 57.7, p = 0.008) compared to controls (191.6 N +/- 74.5 and 161.3 kPa +/- 54.7). Additionally, ankle instability subjects demonstrated significantly higher force-time integral (44.1 N/s +/- 27.3, p = 0.005) and pressure-time integral (35.0 kPa/s +/- 12.0, p = 0.005) compared to controls (23.3 N/s +/- 10.9 and 24.5 kPa/s +/- 9.5). In the lateral forefoot, ankle instability subjects demonstrated significantly greater maximum force (239.9N +/- 81.2, p = 0.004), force-time integral (37.0 N/s +/- 14.9, p = 0.003), and time-to-peak pressure (51.1% +/- 10.9, p = 0.007) compared to controls (170.6 N +/- 49.3, 24.3 N/s +/- 7.2 and 43.8% +/- 4.3).

CONCLUSION:

Using an in-shoe plantar pressure system, chronic ankle instability subjects had greater plantar pressures and forces in the lateral foot compared to controls during jogging.

CLINICAL RELEVANCE:

These findings may have implications in the etiology and treatment of chronic ankle instability.

 

all material copyright 2012 The Homunculus Group/ The Gait Guys. Don’t rip off our stuff. PLEASE ASK 1st!