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Overactivity of Ankle Evertors in those with Chronic Ankle Instability

Tuesday, June 6, 2023 - 5 Likes

Brent Brookbush

Brent Brookbush

DPT, PT, MS, CPT, HMS, IMT

Research Review: Overactivity of Ankle Evertors in those with Chronic Ankle Instability

By Stefanie DiCarrado DPT, PT, MSCS, NASM CPT, CES, PES

Edited by Brent Brookbush DPT, PT, COMT, MS, PES, CES, CSCS, ACSM H/FS

Original Citation: Monaghan, K., Delahunt, E., Caulfield, B. (2006) Ankle function during gait in patients with chronic ankle instability compared to controls. Clinical Biomechanics 21: 168-174 - ABSTRACT

Why is this relevant?: Excessive ankle eversion is a component of ankle/foot dysfunction - often referred to as over-pronation, flat feet, or functional pes planus. This dysfunction often results in ankle instability, and a collapse of the medial longitudinal arch of the foot. It is estimated that 16-30% of individuals present with pes planus (1,2); further, altered ankle mechanics has been associated with increased incident of injury, such as patella tendonitis, knee pain, plantar fasciitis, and low back pain (1,3). It is imperative for movement professionals to understand optimal kinematics and muscle activation patterns at the foot/ankle, and how dysfunction of the foot/ankle may result in dysfunction further up the kinetic chain. This article provides evidence of altered muscle recruitment strategies throughout the gait cycle in individuals with chronic ankle instability.

Illustration of a cross-section of the lower leg with lower extermity muscles and fascia labeled.
Caption: Illustration of a cross-section of the lower leg with lower extermity muscles and fascia labeled.

By Braus, Hermann - Anatomie des Menschen: ein Lehrbuch für Studierende und Ärzte, Public Domain, https://commons.wikimedia.org/w/index.php?curid=29934112

Study Summary

Study Design Cross-sectional Descriptive Study
Level of Evidence Level VI: Evidence from a single descriptive study
Subject Demographics
  • Age:
    • Chronic Ankle Instability (CAI): mean 26.3 + 7.3
    • Control Group (CON): 23.5 + 5.3

  • Gender:
    • CAI: 11 females, 14 males
    • CON: 10 females, 15 males

  • Characteristics:
    • Height (m)
      • CAI: 1.76 + 0.08
      • CON: 1.73 + 0.08

    • BMI
      • CAI: 24.5 + 1.9
      • CON: 22.3 + 2.2

    • Gait Velocity (m/s)
      • CAI: 1.39 + 0.20
      • CON: 1.46 + 0.13

  • Inclusion Criteria:
    • CAI: at least 2 inversion sprains requiring protected weight bearing or immobilization, tendency of the ankle to "give way" during weight bearing, subjective feeling of the ankle being weaker than contralateral ankle or weaker than it was prior to injury
    • CON: Not specified

  • Exclusion Criteria:
    • CAI: History of lower extremity fracture or other condition affecting gait, currently receiving treatment for the ankle, participating in sports
    • CON: History of ankle sprain, lower extremity fracture, other musculoskeletal, neurological, vestibular impairment or condition affecting gait and/or walking velocity

Outcome Measures
  • Recorded for the left leg for CON and unstable ankle in CAI (for those with bilateral dysfunction, recorded for the subjectively weaker ankle)
    • Kinematic and kinetic data from 100ms pre-heelstrike (pre-HS) to 200ms post-HS
      • Kinetic data focused on the type of muscle contraction (concentric, eccentric, isometric) and the joint motion occurring

Results
  • No significant differences in joint kinematics or kinetics at the hip and knee for any plane of motion
  • No significant differences in joint kinematics or kinetics at the ankle in sagittal and transverse planes
  • Kinematics
    • Front plan differences  (100ms pre-HS to 200ms post-HS)
      • Greater inversion (6-7deg) in CAI group than CON

    • Angular velocity
      • 5ms pre & post HS
        • CAI 0.5 rad/s of inversion
        • CON 0.1 rad/s of eversion

      • 150-195ms post HS
        • CAI: eversion moment
        • CON: inversion moment

  • Kinetics
    • 10-40ms, 60-135ms post HS
      • CAI: 0.02-0.06w/kg concentric eversion power generated
      • CON: 0.06-0.08 w/kg eccentric inversion power generated

ConclusionsIndividuals with chronic ankle instability demonstrated increased eversion moment and concentric eversion muscle contractions post heelstrike as compared to healthy controls.  This excessive eversion muscle overactivity is evidence of altered ankle stabilization strategies and suggests correction to a more appropriate strategy may improve overall ankle stability.
Conclusions of the ResearchersThe altered kinematics and kinetics in those with chronic ankle instability are likely to create excessive stress to the ankle joint and surrounding structures during heel strike and the loading response phases of gait which could result in repetitive injury and damage to the ankle itself.

Dr. Brookbush demonstrates and cues a client for an advanced progression of tibialis posterior activation.
Caption: Dr. Brookbush demonstrates and cues a client for an advanced progression of tibialis posterior activation.

Tibialis Posterior Activation

Review & Commentary:

At the time of publication, this study was unique in its 3D kinematic and kinetic analysis of the ankle complex during gait. It remains a unique study in its comparison of individuals with chronic ankle instability (CAI) to healthy controls (CON) during the early stance phase of gait. Previous research focused on jump landing tasks and hypothesis of potential causes, without clinical or experimental confirmation. A strength of this current study is its focus on both kinematic and kinetic data to understand joint motions and the corresponding muscle activity - this is crucial to understanding altered neuromuscular control. The authors provided detailed subject inclusion and exclusion criteria and well described processes and procedures, allowing for replication in future studies. The authors standardized all data collection, using standard equipment protocols, and averaged 10 walking trials to ensure data validity.

This study involved data from a single limb of all subjects; although it may have been interesting to study both ankles in all subjects and compare between individuals, as well as between groups. It was also unfortunate that the current study did not separate attempt to analyze the activity of individual invertor and evertor muscles for more intricate analysis. Further assessment of flexor digitorum longus, flexor hallucis longus , and tibialis posterior activity could have added information that is pertinent to intervention.

Why is this study important?

This article is important as it indicates individuals with CAI demonstrated altered movement patterns and muscle activity during the gait cycle. The CAI group complained of frequent inversion sprains, and demonstrated excessive inversion (both rear and forefoot) during heel strike (HS) and loading response (LR) portions of gait. Excessive motion indicates a poor stabilization strategy, and in this case, poor stabilization of the entire foot and ankle complex.

As an individual progresses from HS to LR, the ankle must become more flexible to accommodate the surface (4). However, too much flexibility results in an instability. We see here that the CON group controlled the ankle and prevented excessive arch collapse (eversion) using the invertors eccentrically. However, the CAI group, displayed concentric evertor activity as the means to stabilize which may lead to excessive eversion and arch collapse over time. Excessive eversion during the stance phase can result repetitive collapse of the entire kinetic chain. As noted in the predictive model of Lower Leg Dysfunction (LLD) , dysfunction at the ankle with a propensity toward eversion, can result in dysfunction of all joints and soft tissue from foot to sacroiliac joint.

How does it affect practice?

Individuals presenting with CAI should be evaluated for altered movement strategies during functional tasks such as walking. Further, assessments of joint motions and muscle testing specific to the limitations presented should be considered. This study may imply that over-activity of the fibularis (peoneal) muscles , and weakness (under-activity) of the tibialis posterior and tibialis anterior should be addressed with release and activation techniques for those with chronic ankle instability.

How does it relate to Brookbush Institute Content?

Over-activity in ankle evertors eventually leads to excessive pronation and collapse of the medial arch during the stance phase of gait and jumping/landing tasks. Seen as feet flatten on the overhead squat assessment , the predictive model of Lower Leg Dysfunction (LLD) notes this compensation pattern as a decrease dorsilflexion (DF) and reduction in frontal plane stabilization resulting in excessive eversion of the subtalar joint. Decreased DF has been found to increase front plane motion at the knee, notably into excessive valgus and may contribute to patellofemoral pain syndrome (7, 8,9,10). Padua et al (2012) found that a heel lift reduced excessive knee valgus during a squat further indicating dysfunction at the ankle affects the frontal plane motion of the knee (8). Further, research has shown improved strength of hip abductor and external rotator muscles resulted in decreased rearfoot eversion during running (6).

The predictive model of LLD notes over-activity in the following hip muscles as they may contribute to a functional knee valgus (knees bow in ), contributing further to calcaneal valgus: Tensor fascial latae (TFL) , biceps femoris , gluteus minimus , anterior adductors . Most applicable to this article is the over-activity found in muscles responsible for ankle eversion: fibularis longus, fibularis brevis , lateral gastrocnemius , and extensor digitorum longus (often mistook for tibialis anterior "soreness" and trigger points). Once the aforementioned over-active muscles are released and/or stretched, the model of LLD recommends activating muscles found to be under active (muscles lengthened by a functional valgus and pronation): Gluteus medius , gluteus maximus , gracilis , semitendinosus , sartorius , and most applicably here related to ankle inversion: medial gastrocnemius , tibialis anterior , tibialis posterior .

Monaghan et al. did not assess arthrokinematic motion, range of motion via goniometry , nor did they perform any manual muscle testing; however, their study did demonstrate excessive inversion with over-activity of the evertor muscles and under-activity in the invertors in those with chronic ankle instability. This may seem counter-intuitive, as excessive evertor activity should result in excessive eversion. It is our hypothesis that the excessive inversion is either a learned strategy in an attempt to shift the center of mass lateral to the medial longitudinal arch (similar to gluteus medius weakness resulting in a trendelenburg gait pattern), or that laxity in the lateral ligaments of the ankle results in a reduction in the overall force contributing to ankle eversion.

Based on the combined findings of this study and the predictive model for LLD , it may be implied that a corrective intervention for CAI include inhibition techniques for the evertors and activation techniques for the invertors, with special attention paid to reactive eccentric control of eversion (tibialis posterior reactive activation ) and integrative exercise mimicking functional tasks. Techniques, addressing arthrokinematic dysfunction, as well as dysfunction of the knee and/or hip may be necessary for complete resolution of dysfunction.

The videos below demonstrate proper ankle evertor inhibition (also toe flexor inhibition), ankle invertor activation, and an arch control integrative intervention.

Gastroc Soleus Manual Release

Fibularis Manual Release

Calf and Fibularis Peroneal Manual Stretching

Tibialis Posterior Activation Progression

Tibialis Posterior Reactive Activation

Sources

  1. Williams DS, McClay IS, Hamill J. Arch structure and injury patterns in runners. Clin Biomech2001;16:341–7.
  2. Pes planus, Retrieved from http://medical-dictionary.thefreedictionary.com/pes+planus
  3. Kosashvili Y, Fridman T, Backstein D, et al. The correlation between pes planus and anterior knee or intermittent low back pain. Foot Ankle Int 2008;29:910-3.
  4. Perry, J. (1992) Gait Analysis: Normal and pathological function. New Jersey: SLACK Incorporated.
  5. Klein, P., Mattys, S., & Rooze, M. (1996). Moment arm length variations of selected muscles acting on talocrural and subtalar joints during movement: An in vitro study. Journal of biomechanics, 29(1), 21-30
  6. [Snyder, K. R., Earl, J. E., O’Connor, K. M., & Ebersole, K. T. (2009). Resistance training is accompanied by increases in hip strength and changes in lower extremity biomechanics during running. Clinical Biomechanics, 24(1), 26-34)](https://brentbrookbush.com/articles/research-corner/ankle-and-foot/training-hip-musculature-results-in-improved-lower-extremity-biomechanics-during- running/?from=138)
  7. Macrum et al. (2012) Effect of limiting ankle-dorsiflexion range of motion on lower extremity kinematics and muscle-activation patterns during a squat. Journal of Sport Rehabilitation. 21, Pg 144-150
  8. Padua, D. A., Bell, D. R., & Clark, M. A. (2012). Neuromuscular characteristics of individuals displaying excessive medial knee displacement. Journal of athletic training, 47(5), 525
  9. Mauntel, T., Begalle, R., Cram, T., Frank, B., Hirth, C., Blackburn, T., & Padua, D. (2013). The effects of lower extremity muscle activation and passive range of motion on single leg squat performance. Journal Of Strength And Conditioning Research /National Strength & Conditioning Association, 27(7), 1813-1823

© 2016 Brent Brookbush

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