1. Clinical Management of Biomechanical Foot/Ankle Problems
BIOMECHANICS REVIEW
Edmund M. Kosmahl, PT, EdD
© 2001 Edmund M. Kosmahl

2. Supination and Pronation
Plantarflexion
Adduction
inversion
Pronation
Dorsiflexion
Abduction
Eversion
Graphic © 1989 Edmund M. Kosmahl.

3. JOINTS AND FUNCTIONAL UNITS

4. Ankle
Graphic © 1989 Edmund M. Kosmahl.

5. Ankle
Minimum range required for gait = 10o with knee extended and subtalar joint neutral
Graphic © 1977 Clinical Biomechanics Corp.

6. Subtalar Average range of motion 30o (calcaneal inversion/eversion)
2/3 calcaneal inversion, 1/3 calcaneal eversion
Minimum 8o – 12o required for gait
Graphic © 1989 Edmund M. Kosmahl.

7. Midtarsal Longitudinal and oblique axes
Available range depends on the position of the subtalar joint
Graphic © 1977 Clinical Biomechanics Corp.

8. Midtarsal Axes Longitudinal Oblique Mostly inversion/eversion
Range about 4o – 6o
Oblique
Mostly plantarflexion-adduction / dorsiflexion-abduction
Range unknown
Graphic © 1977 Clinical Biomechanics Corp.

9. First Ray Average dorsiflexion 5 mm
Ranges of plantarflexion and dorsiflexion should be equal
Graphic © 1989 Edmund M. Kosmahl.

10. Fifth Ray
Graphic © 1989 Edmund M. Kosmahl.

11. First Metatarsophalangeal Joint
Minimum 65o dorsiflexion required for gait
Dorsiflexion range requires plantarflexion of 1st ray
Graphic © 1977 Clinical Biomechanics Corp.

12. MUSCLE FUNCTION

13. Muscle Function
Gastrocnemius, Soleus, Tibialis posterior, Flexor Digitorum Longus, Flexor Hallucis Longus
Supinators, or pronation controllers

14. Muscle Function Peroneus Longus and Brevis
Evertors of foot or supination controllers
Peroneus longus has special function . . .

15. Peroneus Longus
Plantarflexes 1st ray during terminal stance to allow dorsiflexion of 1st MTP
Graphic © 1977 Clinical Biomechanics Corp.

16. Muscle Function
Tibialis Anterior, Extensor Hallucis Longus, Extensor Digitorum Longus, Peroneus Tertius
Dorsiflexors of ankle or plantarflexion controllers
TA and EHL balance EDL and PT to neutralize inversion and eversion

17. Adductor Hallucis Transverse Head
AKA Transverse Pedis
Prevents forefoot splay during terminal stance as long as 1st ray is plantarflexed
Graphic © 1977 Clinical Biomechanics Corp.

18. Adductor Hallucis Transverse Head
Prevents forefoot splay during terminal stance as long as 1st ray is plantarflexed
(Subtalar supinated, peroneus longus)
Graphic © 1977 Clinical Biomechanics Corp.

19. Ideal Alignment “Criteria for Normalcy” Rarely seen clinically
Graphic © 1984 American Physical Rehabilitation Network

20. Ideal Alignment (non-weight bearing)
Malleolar Torsion 13o to 18o external
Graphic © 1989 Edmund M. Kosmahl.

21. Ideal Alignment (non-weight bearing)
Ankle dorsiflexion minimum 10o with knee extended and subtalar joint neutral
Ankle plantarflexion minimum 20o
Graphic © 1990 FA Davis Co.

22. Ideal Alignment (non-weight bearing)
Subtalar range 8o to 12o minimum
Subtalar neutral position – calcaneal bisection and distal 1/3 leg bisection parallel
Graphic © 1984 American Physical Rehabilitation Network

23. Ideal Alignment (non-weight bearing)
Midtarsal joint – plantar plane of forefoot parallel to plantar plane of rearfoot (and perpendicular to calcaneal bisection) when subtalar is neutral and midtarsal pronated maximally
Graphic © 1984 American Physical Rehabilitation Network

24. Ideal Alignment (non-weight bearing)
First Ray – equal range (about 5mm) above and below plane of 2nd met when subtalar is neutral and midtarsal pronated maximally
Graphic © 1977 Clinical Biomechanics Corp.

25. Ideal Alignment (non-weight bearing)
Fifth Ray – equal range above and below plane of middle three meets when subtalar is neutral and midtarsal pronated maximally
Graphic © 1977 Clinical Biomechanics Corp.

26. Ideal Alignment (weight bearing)
Distal 1/3 leg bisection vertical
Knee, ankle, subtalar in transverse plane parallel to floor
Subtalar neutral
Calcaneus bisection verticlal
Midtarsal axes locked in maximally pronated position
Forefoot and rearfoot parallel to floor and each other
Graphic © 1984 American Physical Rehabilitation Network

27. REARFOOT AND LEG PATHOMECHANICS

28. Muscle Dysfunction Pronators Supinators
Peroneus longus and brevis, extensor digitorum longus, peroneus tertius
Charcot-Marie-Tooth disease (peroneal atrophy)
Weakness leads to supinated rearfoot (cavus foot)
Supinators
Gastrocnemius, soleus, tibialis posterior, flexor digitorum longus, flexor hallucis longus, tibialis anterior
Weakness leads to pronated rearfoot (flatfoot)

29. Abnormal Osseous Structure
Most common causes of foot/ankle pathomechanics
Deviations from Ideal Alignment
Graphic © 1984 American Physical Rehabilitation Network

30. Abnormal Osseous Structure
Calcaneus / Leg Relationships
(open chain)

31. Subtalar Varus
Bisection of calcaneus inverted with respect to leg when subtalar joint is neutral
Graphic © 1984 American Physical Rehabilitation Network

32. Subtalar Valgus
Bisection of calcaneus everted with respect to leg when subtalar joint is neutral
Graphic © 1988 Williams & Wilkens

33. Abnormal Osseous Structure
Calcaneus / Floor Relationships
(closed chain)

34. Rearfoot Varus or Valgus
Bisection of calcaneus inverted (varus) or everted (valgus) with respect to floor
Rearfoot
Varus
Graphic © 1988 Williams & Wilkens

35. Tarsal Coalition Abnormal union between two or more tarsals
Syndesmosis – fibrous
Synchondrosis – cartilage
Synostosis – bony (usually no motion or irritation)
Compensation = persistent pronation
Graphic © 1988 Williams & Wilkens

36. Tibial Varum or Valgum
Distal 1/3 of tibia bowed toward midline (varum) or away from midline (valgum)
1o to 2o is common
Varum  calcaneal inversion  rearfoot varus
Graphic © 1988 Williams & Wilkens

37. Abnormal Osseous Structure
Forefoot / Rearfoot Relationships

38. Forefoot Varus
Plantar plane of forefoot inverted with respect to plantar plane of rearfoot
ROM of midtarsal joint is normal (position is incorrect)
Graphic © 1984 American Physical Rehabilitation Network

39. Forefoot Valgus
Plantar plane of forefoot everted with respect to plantar plane of rearfoot
ROM of midtarsal joint is normal (position is incorrect)
Graphic © 1984 American Physical Rehabilitation Network

40. Forefoot Supinatus
Fixed varus position caused by soft tissue adaptation
ROM of midtarsal joint is limited
Result of ambulating on everted calcaneus
Graphic © 1984 American Physical Rehabilitation Network

41. Abnormal Osseous Structure
Forefoot Relationships

42. Plantarflexed First Ray
More plantarflexion ROM than dorsiflexion ROM
Graphic © 1984 American Physical Rehabilitation Network

43. Metatarsus Primus Elevatus (dorsiflexed 1st ray)
More dorsiflexion ROM than plantarflexion ROM
Graphic © 1989 Edmund M. Kosmahl.