Mechanics and control of the
pes planus versus normal foot
during jumping and landing
Reporter: Reportor : Zong-Shein Chen
Supervisor : Sai-Wei Yang
1
Introduction
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Pes planus (flat foot)
- the medial longitudinal arch of foot is lower
than established normal parameters
~ Forrester D et al. Imaging of the foot and ankle;1988
- Occurs in approximately 15% of the
population
~ Harris R and Beath T. J Bone Joint Surg;1948
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The terms of pes planus :
- Flexible : An observable medial arch during
nonweightbearing and a flattening of the arch
during weightbearing
- Rigid : A stiff, flattened arch on and off
weightbearing
~ Lee MS et al. J Foot Ankle Surg; 2005
3
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The stages of pes planus :
- In clinically and functionally, the rearfoot of flat
foot subjects is valgus and the forefoot is varus
~ Bertani A et al. Clin Biomech. 1999
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~ Magee DJ. Orthopedic Physical
Assessment; 2002
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Abnormal biomechanical behaviors
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The MLA collapses right down
Most of the plantar surface of foot contact with
the ground
More strain on the plantar aponeurosis
Facilitating dorsiflexion
Unlocking of the midtarsal joint
~ Prost WJ. Fam Physician; 1979
5
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Greater inversion ankle moment
Greater peak plantarflexion ankle moment
Less forefoot adduction
Less forefoot total transverse plane ROM
~ Hunt AE et al. Clin Biomech; 2004
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Greater foot pressure under the second and
third metatarsal heads
Greater foot pressure under the subhallucal
area
~ Hunt GC. Examination of lower-extremity dysfunction; 1990
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Injuries relate to pes planus
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Pes planus are associated with a higher risk of
injury among physically active people
~ Kulthanan T et al. J Med Assoc Thai; 2004
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Subjects with pes planus feet exhibited greater
incidences of soft tissue and medial foot injuries
and knee injuries
~ Williams DS et al. Clin Biomech; 2001
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Sesamoiditis
Plantar fasciitis
Achilles tendinitis
Medial shin pain
Patello-femoral joint pain
Metatarsal stress fractures
Navicular and fibular stress fractures
~ Hunt AE et al. Clin Biomech; 2004
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Posterior tibialis tendon dysfunction
- Painful pes planus can often be associated
with Posterior Tibial Tendon Dysfucntion (PTTD)
- The posterior tibial muscle has a significant
role in supporting the medial longitudinal arch
~ Kulig K et al. Med Sci Sports Exerc; 2005
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Risk sports for foot and ankle injury
~ DeLee et al. Br J Sports Med; 2003
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Jumping and landing
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Jump-landing protocols have been used to
measure postural sway
In an attempt to reduce the landing force the
body must anticipate the landing and prepare for
it by increasing muscle stiffness
~ McKinely P, Pedotti A. Exp Brain Res ;1992
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Further reduction of landing force can be
accomplished by allowing the knee and hip to
flex more which increases the time of landing
providing an attenuation in kinetic energy
~ McNair P et al. Br J Sports Med; 2000
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Effect of Foot Orthotics on Quadriceps and Gluteus
Medius Electromyographic Activity During Selected
Exercises
~ Hertel J, Sloss BR et al. Arch Phys Med Rehabil. 2005;86:26-30
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Design: Experimental, controlled
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Participants: Thirty healthy young adults, 10 with
each foot type
- Foot type was subjectively categorized by a
clinician experienced in lower extremity
biomechanic evaluation
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Interventions
- 3 foot-type groups : pes planus, pes cavus, pes
rectus
- Each tested in 4 orthotic conditions : no orthotic,
7° medial rearfoot post, 4° lateral rearfoot post,
and neutral rearfoot post
- Performing 3 different exercises : single-leg
squatting, lateral stepdown, and maximum
vertical jump
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Outcome Measure : Surface EMG activity for the
vastus medialis, vastus lateralis, and gluteus
medius during exercises
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Results : Less vastus lateralis activity was found
with the vertical jump with all orthotic conditions,
regardless of foot type
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Purpose
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Few investigations focus on the jumping and
landing biomechanical behaviors of pes planus
subjects
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The purpose in this study is to explore the
jumping and landing biomechanical behaviors of
pes planus subjects
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Hypothesis
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The jumping and landing biomechanical
behaviors are different between pes planus and
normal foot subjects, including COP excursion
way, magnitude and direction of GRF, relative
motion of foot-leg-knee and the EMG activity of
the muscle
Methods - Participants
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Thirty adult, aged from 18 to 25 years old
Inclusion criteria :
- arch index > 0. 26
- flexible pes planus
~Williams DS et al. 2000
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Exclusion criteria :
- Acute foot injuries
- Previous osseous foot surgery
- Diagnosed with inflammatory arthritis, diabetes
mellitus, congenital defects or neuromuscular
disease
Instrumentation
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Vision motion analysis system ~ VICON : to
collect kinematic data
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AMTI force plate : to collect kinetic data
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Surface EMG : to collect muscle activation data,
tibialis posterior, peroneus brevis and longus,
medial and lateral gastrocnemius, vastus
medialis and lateralis, biceps femoris
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Procedures
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While jumping, subjects were instructed to hold
their hands at their waist to restrict arm movement
substitution for jump effort
Four conditions, and 3 trials for each condition :
1. Vertical jump with both legs at maximum effort and to
land with both legs
2. Vertical jump with both legs at maximum effort and to
land on the dominant leg
3. Forward jump with both legs and to land with both legs
4. Forward jump with both legs and to land on the
dominant leg
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Data analysis
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Descriptive statistics and two-way ANOVA tests
will be used to compare the difference of testing
order effects and four experimental conditions
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Tukey’s post-hoc test will be used when an
overall significant differences are found
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An alpha level of 0.05 will be used to test for
significance
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Thanks for your attention
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Reference
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Lee MS, Vanore JV et al. Diagnosis and Treatment of Pediatric Flatfoot. J
Foot Ankle Surg. 2005;43:341-373
Hunt AE, Smith RM. Mechanics and control of the flat versus normal foot
during the stance phase of walking. Clin Biomech. 2004;19:391-397
Ledoux WR, Hillstrom HJ. The distributed plantar vertical force of neutrally
aligned and pes planus feet. Gait posture. 2002;15:1-9
Prost WJ. Biomechanics of the foot. Fam Physician. 1979;25:821-31
Hunt GC. Orthopaedic and sports physical therapy. Examination of lowerextremity dysfunction. Second Edition. 1990:395-421
Williams DS, McClay IS et al. Arch structure and injury patterns in runners.
Clin Biomech. 2001;16:341-347
Kulig K, Burnfield JM et al. Effect of foot orthoses on tibialis posterior
activation on persons with pes planus. Med Sci Sports Exerc;2005:24-29
Hertel J, Sloss BR et al. Effect of Foot Orthotics on Quadriceps and Gluteus
Medius Electromyographic Activity During Selected Exercises. Arch Phys
Med Rehabil. 2005;86:26-30