1. Clinical Foot and Ankle Biomechanics Overview of course By Paul Harradine (Podiatrist)
Fiona Holdcroft
May 2009

2. Session Overview Functional anatomy:
Basic terminology
The ‘normal’ foot
The abnormal foot
Gait
Biomechanical foot and ankle assessment
Our role in treatment
Summary/conclusions

3. The ‘Normal’ Foot The unified theory 3 previous podiatric theories
All disagree in normal, abnormal and treatment methodology
All achieved clinical results
Unified theory combines the above
Foot Morphology (1970), Tissue Stress Theory (1980), Sagittal plane facilitation theory (1980)

4. Basic Terminology Pronation (Arch lowering) Supination (Arch Rising)
Position of Eversion, Abduction & Dorsiflexion
Supination (Arch Rising)
Position of Inversion, Adduction & Plantarflexion
Varus - Inversion
Valgus - Eversion
Forefoot - Structures distal to midtarsal joint
1st Ray
1st metatarsal, medial cuneiform & navicular
NOT hallux

5. Functional Anatomy Ankle joint Talocrural Subtalar joint
Midtarsal joint
1st Ray/MTPJ
Talocrural – PF/DF. As DF talus pushes into tibia mortis – if stiff here can loose 8 degrees DF thus can mob them
Subtalar – Pron/Supination & inversion/eversion (2:1 ratio, 20 vs 10 degrees) Soft end feel vs bony end feel) . Forms rear foot.
Mid tarsal joint - Functional unit consisting two separate joints (calcaneo-cuboid & talo-navicular). Very floppy joint (i.e. if cup heal to stabilize rear foot can wobble MTJ in all directions ->decreased stability but ability to adapt to different surfaces
1st ray - triplanar but clinically PF/DF

6. Normal foot function
Axis normally in line with 2nd toe (Subtalar joint ensures this with level of pron/supn)

7. Abnormal foot function
Medial axis
Pronated
Lateral axis
Supinated

8. Ground Reaction Force Neutral foot position provides equal force
Change in foot axis increases ground reaction force on one side causing foot to tilt
i.e. medial movement of axis increases lateral pressure so foot everts resulting in pronation
Therefore if have pronated foot want to put orthotic on medial heal to increase ground reaction force here to get equilibrium and reduce pronation

9. Interaction of 1st ray and 1st MTPJ
Try:
PF/DF 1st ray
PF/DF hallux
DF 1st ray then DF hallux
Normal interaction
ROM 1st MTPJ is dependant on position of 1st ray
1st ray has to PF (drop) to allow translation
Can get functional limitation of DF at hallux with lack of 1st ray PF
If DF (push up) 1st ray ->decreased ext hallux
Arch filler not good as pushes 1st ray up -> decreased great toe mvt

10. Gait Cycle Foot responds to the hip during gait cycle
As MR hip foot pronates
As LR hip foot supinates
Heal strike -> stance -> toe off
Hip MR Hip LR
Pronation Supination
Thus clinically OA hip cant pronate in standing and weak gluts leads to pronation

11. Stability in the gait cycle
Required during stance phase
Heal strike
Reverse windlass mechanism
Pronate
Arch lowers & lengthens
Plantar structures become taut
Pulls joints together
Increased stability
Do also have additional stabilising factors e.g. long and short plantar ligaments and the spring ligaments and intrinsic foot m/s cross mid tarsal joint thus strengthening these will decrease pronation

12. …however this decreases toe flexion
stand with foot pronated & try and PF hallux
Toe off
Windlass mechanism
Foot supinates
Arch rises
(Potential to loose tension in plantarfascia and thus stability)
Tension maintained in plantarfascia through ‘winding’ of the windlass around 1st MTPJ i.e. PF hallux
If just let arch rise plantar facia will loose tension/slacken thus decreasing stability (when we need it most)
i.e. have to DF hallux to maintain tension in plantarfascia thus maintaining stability

13. Rocking mechanism
To allow smooth transfer of weight from heal strike to toe off
3 mechanisms:
Heal
Rounded underside facilitates forward momentum
Passive knee flexion as tib ant eccentrically fires to decelerate motion
Ankle DF
DF of digits
Preferably hallux (60%)
Allows hip extension
Ankle – need 10 degrees DF, controlled through eccentric calf activity (N.B as knee is already flexed)
DF digits - hallux ->ensures windlass mechanism

14. Over pronation To hard To far
Can not re-supinate or LR at hip
Gait compensation e.g. abductory twist, reduced hip rotation
To far
Lower limb functional malalignment
Increased MR hip ‘squinting patella’
Increased plantarfascia stress
Gait compensation e.g. side sway, excessive pelvic rotation, decreased hip extension, trunk flexion, abductory twist, MTJ DF, 1st IPJ DF, lateral column propulsion
Functional hallux limitus & reduced 3rd rocker
Abductor twist – MR heal to give LR at hip
Reduced LR hip – decreased pelvis rotation, forward lean, decreased arm swing
Functional halloos limitus via reverse windlass mechanism
Side sway – moves foot axis laterally
Lateral column propulsion – walk on lateral border i.e. 5th toe. Often seen as wear on lateral side of shoes
NB: altered gait can be due to other factors e.g. decreased hip extension, weak gluts

15. What causes pronation? Muscle activity e.g. weak gluts
Increased external pronatory forces
Obesity
Running
Ankle Equinus
Reduced DF ROM (<10 degrees with foot in subtalar neutral)
Reduced 2nd rocker
Weak gluts e.g. post hip surgery
Obesity increases pronation as increased mass increases pronation force therefore decreased ability to re-supinate

16. Compensation mechanism
Foot morphology
Rearfoot varus
Rearfoot inverted in relation to lower 1/3 of leg
Forefoot varus
Forefoot inverted in relation to rearfoot
Forefoot Valgus
Forefoot everted in relation to rearfoot
PF 1st ray
2 forefoot angles: 1-5 &2-5
Compensation mechanism
2-5 is true angle, 1-5 hides it (due to PF 1st ray)

17. ARCH height means nothing - It is irrelevant -
Important thing is reserve of pronation

18. Foot assessment LL assessment in supine Subtalar neutral
Pronation tests
Supination Resistance Test
Maximum Pronation Test
Navicular Drop Test
Hubschers Test
STJ Axis Position
Gait analysis

19. LL assessment in supine
Leg length
Malleolus position pre and post ‘sit up’
MR/LR at hips
Knee extension
Position of tibial tuberosity vs patella
Tibial torsion
?knee hyperextension
Tibial tuberosity ideally under patella/in line
?bowing of tibia

20. Subtalar neutral Patient prone Feel talus position with ‘inside hand’
Move foot to find neutral with ‘outside hand’
In subtalar neutral assess for
ROM DF?
Rearfoot or forefoot varus/valgus?
Position of 1st ray?

21. Pronation tests
Quick guide into relationship between patients foot function and symptoms
5 tests
Help to answer the question
How hard is the patient pronating?
How far is the patient pronating?
Is there a functional hallux limitus?
Does my patient need an onward podiatry referral?
Does my patient need orthotics?
Possible false negative BUT not false positive due to static assessment of dynamic structure

22. Supination Resistance Test
Assesses force required to re-supinate STJ
With patient standing try and lift arch with moderate force i.e. supinate foot
Assess resistance
Easy: abnormally small pronatory forces ?supinator
Moderate: Normal
Hard: Abnormally large pronatory forces

23. Maximum Pronation Test
Assesses reserve of pronation, and thus if patient is maximally pronated irrespective of arch height
With patient standing ask them to roll down their arches. Assess for calcaneal eversion (from behind):
< 2 degrees rearfoot eversion -> no reserve of pronation, thus maximally pronated
>2 degrees rearfoot eversion ->reserve of pronation, thus not maximally pronated

24. Navicular Drop Test
Assesses amount of pronation relevant to STJ, not arch height
With patient standing record height of navicular tubercle with neutral axis (from behind). Repeat with patient relaxed
>10mm drop indicates abnormally pronated foot position

25. The Hubscher Test Assesses for functional hallux limitus
With patient standing attempt to passively DF hallux
Grade on scale 0-3:
0: Nil DF (abnormal - ?pronator)
1: Slight DF (abnormal - ?pronator)
2: DF with resistance. Slight arch raising with limited MR leg (normal)
3: DF with limited resistance. Complete arch rising with obvious MR leg (abnormal - ?supinator)

26. STJ Axis Position Allows estimation of joint axis position
With patient standing palpate talus head and estimate angle of axis by imagining perpendicular line to talus
Medial axis indicates ?pronation
Axis towards 2nd toe indicates neutral foot position
Lateral axis indicates ?supination

27. Pronatory Gait Compensations
Abductory twist
Reduced pelvic rotation
Trunk flexion/forward lean
Decreased arm swing
Increased side sway
Excessive pelvic rotation
Decreased hip extension
MTJ DF
1st IPJ DF
Lateral column propulsion
Abductor twist – MR heal to give LR at hip
Reduced LR hip – decreased pelvis rotation, forward lean, decreased arm swing
Side sway – moves foot axis laterally
Excessive pelvic rotation – AP/PA. Move pelvis due to decreased ability to rotate hips
Decreased hip extension – reduced 3rd rocker
MTJ DF – Rock over MTJ
1st IPJ DF – Hyperextend great toe to rock through
Lateral column propulsion – walk on lateral border i.e. 5th toe. Often seen as wear on lateral side of shoes
NB: altered gait can be due to other factors e.g. decreased hip extension, weak gluts (-> increased pronation-> decreased 3rd rocker)

28. Our role in treatment Exercises: aim to decreases pronatory forces
LR hip strengthening
Stretches for ankle equinus
Intrinsic foot muscle strengthening
Proprioception training
Mobilisations: aim to increase ROM to restore normal gait
TCJ
MTJ
1st MTPJ

29. Taping/padding: To reduce pronatory forces
Plantarfascia taping
Trial felt medial heal wedge
Trial felt 1st ray cut outs
Helps recognise when orthotics may be beneficial
Padding – build up medial heal to decrease pronatory force -> decreased pronation. Stand someone on orthotic and review great toe extension

30. Orthotics
Aim to reduce pronatory forces and facilitate medial column propulsion
Equalise ground reaction force
Bring axis from medial position to 2nd toe
Level the see-saw
Facilitate ‘normal’ gait
Use rearfoot posting with medial heal support +/- 1st ray cut off NOT arch support
Need to recognise when to use custom or non custom orthotics

31. Custom vs non-custom orthotics
Immediate provision
Inexpensive
Bulky
Limited modification to patient
Often 1st ray impingement
Custom
Modified for patient
Required for complex patients
Outcome reviewed
Less bulky
Wait to see podiatry
More expensive
NB Poorly fitting orthotics can cause functional hallux limitus
AND Never alter an orthotic, refer back to prescriber

32. The Runner Running is not an accelerated form of walking: Therefore
Increased GRF (2.5-3x body weight)
Increased frequency of heal strike
Increased limb varus
Therefore
Increased need to reduce pronatory forces e.g. with orthotics, strengthening
Need to check outcomes dynamically
Look at footwear
Walking GRF = xbody weight

33. Trainers Many varieties 3 Classification Neutral Weight Stability
Motion Control Control
Mizuno Waverider 11
Brooks GTS Adrenalin 8
Brooks Beast/Ariel

34. Upper support Flexion stability
If push down on medial border of shoe it should provide support and not compress down
Flexion stability
If push up on distal end of shoe should flex at MTPJ NOT mid foot
Good flexion stability
Bad flexion stability
Poor upper stability

35. Summary Foot acts as a see-saw and responds to GRF
Normal foot function during gait:
Heal strike and the 1st rocker
MR hip and foot pronation
Reverse windlass mechanism
2nd rocker to allow stance
LR and foot supination
3rd rocker for toe off
Windlass Mechanism and medial column propulsion
Hip and knee extension to progress to swing phase

36. Screen for over pronation with 5 key tests Recognise when
Foot position may be impacting on symptoms
Orthotics may be appropriate
Referral to podiatry is indicate