More than you ever wanted to know about the foot

1. More than you ever wanted to know about the foot MAJ Joel L. Shaw Sports Medicine 24 May 2007

2. Overview • Describe foot and ankle joints • Joint actions during running • Related pathology • How to prescribe running shoes

3. Foot function • 1. Accept vertical forces during heel strike • 2. Absorb and dissipate these forces across a flexible mid- and forefoot during pronation • 3. Provide propulsion as the foot becomes a rigid lever with resupination and toe-off

4. Articulations • Subtalar • Talocalcaneonavicular • Calcanealcuboid • Midtarsal • Tarsometatarsal • Metatarsophalangeal • Interphalangeal

5. Subtalar • Triplanar • Supination vs. Pronation • Bones: inferior talus, superior calcaneus • Alternating concave-convex facets limit mobility • Ligaments- talocalcaneal, interosseous talocalcaneal, cervical

6. Subtalar joint • Supination • Inversion by calcaneus • Abduction by talus. • Dorsiflexion by talus • Talar abduction causes external rotation of the tibia • Position of most stability

7. Subtalar joint • Pronation • Eversion by calcaneus • Adduction by talus • Plantarflexion by talus • Talar adduction causes internal rotation of the tibia • May increase Q angle • Increased flexibility and shock absorption

8. Subtalar joint • Clinical significance • Mobility • Shock absorption • Stability

9. Midtarsal joint • Functional joint- includes talonavicular and calcaneocuboid joint • Triplanar supination/pronation- primarily DF/PF and abd/add • Navicular- highest point of medial arch

10. Midtarsal joint • Assist pronation/supination of the subtalar joint • Maintain normal weight bearing forces on the forefoot • Control/communication between rear foot and forefoot

11. Metatarsophalangeal joint • Biplanar- mostly dorsiflexion/plantarflexion with 10 degrees of abduction/adduction • Dorsiflexion- allows body to pass over foot while toes balance body weight during gait • Plantarflexion- allows toes to press into ground for balance during gait

12. First ray • Functional joint • Bones- Navicular, 1st Cuneiform, 1st Metatarsal • Plantarflexion at late stance to assist 1st MTP dorsiflexion • Peroneus longus and abductor hallicus brevis muscles

13. Plantar fascia • Causes tension along the arch • Supination facilitated as arch heightened • Windlass effect

14. Windlass effect • Webster’s: machine for pulling a rope around a drum. Pulley system to lift anchor in a boat.

15. Windlass effect • Tension in the aponeurosis secondary to toe extension elevates the arch by acting as a pulley around which the aponeurosis is tightened.

16. Ligaments • Spring ligament • Tension wire which helps maintain arch • Helps rigidity during propulsion • Long plantar ligament • Plantar aponeurosis • Short plantar ligament

17. Function of arches • Stability • Distribution of weight • Mobility • Dampens shock of weight bearing • Adaptation to changes in support surfaces • Dampening of superimposed rotations

18. Stance phase 40% of gait cycle 2 phases Absorption Propulsion Swing phase 60% of gait cycle 2 phases Initial swing (ISW)- 75% Terminal swing (TSW)- 25% Running gait

19. Double float Stride length Step length Cadence Velocity=stride length x cadence Running gait

20. Running gait • Kinematics vs. Kinetics • Kinematics- motion of joints independent of forces that cause the motion to occur • Kinetics- study of forces that cause movement, both internally and externally • Internal- muscle forces • External- ground reactive forces

21. Ankle/foot kinematics • Ankle joint • Dorsiflexion/plantarflexion • Foot joints • Triplanar • Pronation and supination

22. Running gait- ankle kinematics • Absorption and midstance • Rapid dorsiflexion (response to increased hip and knee flexion) • Decreased plantarflexion in running decreased supinationcause of increased running injuries??

23. Running gait- foot kinematics • Subtalar motion determined by muscular activity and ground reactive forces • Midtarsal motion determined by subtalar position

24. Calcaneus/talus supination Increase midtarsal obliquity Lock joint “Rigid lever” During propulsion and ISW Calcaneus/talus pronation Parallel midtarsal joints Increased ROM “Mobile adapter” Mid stance Running gait- midtarsal joint

25. Axis of transverse tarsal joint O'Connor FG, Wilder RP: Textbook of Running Medicine, McGraw Hill Companies, 2001. Page 13.

26. Running gait- foot kinematics • Absorption • Pelvis, femur, tibia internally rotate • Eversion and unlocking of subtalar joint • Pronation of midtarsal joints • Allows mobility and shock absorption. • Able to adapt to ground surface. • Plantar fascia- relax medial arch

27. Running gait- foot kinematics • Propulsion • Pelvis, femur, tibia externally rotate • Inversion/locking of subtalar joint • Supination of forefoot • Plantar fascia- increase medial arch stability and invert heel • Metatarsal break- promote hindfoot inversion and external rotation of leg

28. Running gait- foot kinetics • External forces- ground reactive forces • Vertical- 3-4 times body weight • Fore-aft- 30% of body weight • Medial-lateral- 10% of body weight • Newton’s third law • Internal forces- muscle forces

29. External forces • Foot strike pattern • Forefoot Midfoot Rearfoot

30. Rearfoot striker • 80% of runners • Initial contact- posterolateral foot • Center of Pressure (COP) • Outer border of rear footprogresses along lateral borderthen across forefoot medially toward 1st and 2nd metatarsal head

31. Midfoot strikers • Most other runners • Initial contact- midlateral border of foot • COP • Lateral midfootprogresses posteriorly (corresponds to heel contact)rapidly moves to the medial forefoot

32. Evaluation of running injuries • Training log • Shoe examination • Arch appraisal • Gait analysis • Running shoe prescription

33. Training log • Weekly mileage • Transition point • Increase in distance or intensity • Increase in mileage >10% per week • Change in terrain or running surface

34. Shoe examination • Current running shoes • Age (days and miles) • Replacement frequency • New brand or model? (change biomechanics)

35. Shoe examination • Outsole wear • Lateral heel vs. inside heel vs. lateral sole • Midsole wear • Heel counter tilt • Midsole wrinkling, tilt, or decomposition

36. Shoe wear • Based on foot strike pattern, initial contact, and center of pressure • Neutral gait • Wear on lateral aspect of heel • Uniform wear under the toes

37. Shoe wear • Overpronator • Excessive wear on medial portion of heel and forefoot • Underpronator • Excessive wear on lateral heel • Wear on entire lateral portion of the outersole

38. Arch appraisal • Standing arch contour • “Wet test” • Static evaluation=running evaluation?

39. Biomechanical function • Required functions of locomotion • Adaptation • Shock absorption • Torque conversion • Stability • Rigidity

40. Biomechanical assessment • Video gait analysis • Always base on running gait, not arch height • Evaluate shoe wear

41. Gait analysis • Behind- location of heel strike, foot motion during single stance, foot engaged at push-off • Side- gastroc-soleus flexibility, great toe dorsiflexion • Treadmill-based analysis • Force plate analysis

42. Neutral gait • Level Heel Throughout Gait Cycle • 90 Degree Medial Angle Throughout Gait Cycle

43. Intrinsic abnormalities • Pes cavus- abnormal supination • Pes Planus- abnormal pronation

44. Normal Late stance phase Provides rigidity, support, propulsion Facilitates lower leg external rotation Abnormal Minimal pronation at subtalar joint Little drop of medial longitudinal arch Supination

45. Abnormal supination- signs • Lateral Leaning Foot Surface Placement • Inflexible Foot • Callus- 1st and 5th metatarsal heads • Clawing of 4th and 5th digits

46. Stable and rigid foot Lacks flexibility and adaptability Poor gastroc-soleus flexibility Achilles tendonitis Plantar fasciitis Poor shock absorption Tibial and femoral stress fractures Abnormal supinators

47. Normal Early in stance phase Provides flexibility, adaptability and shock absorption Facilitates lower leg internal rotation Abnormal Continues throughout stance phase Pronation

48. Mild Overpronation- signs • Slightly Greater than 90 Degree Angle Throughout Gait Cycle • Medial Leaning Foot Surface Placement • Some Ankle Instability/ unstable position

49. Severe overpronation- signs • Significant Medial Leaning of Surface Foot • Great Instability • Excessive internal tibial rotation • Increased medial stress

50. Overpronators • Patellofemoral pain • Popliteal tendonitis • Posterior tibial tendonitis • Achilles tendonitis • Plantar fasciitis • Metatarsal stress fracture