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

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

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

Articulations Subtalar Talocalcaneonavicular Calcanealcuboid Midtarsal Tarsometatarsal Metatarsophalangeal Interphalangeal

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

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

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

Subtalar joint Clinical significance Mobility Shock absorption Stability

Midtarsal joint Functional joint- includes talonavicular and calcaneocuboid joint Triplanar supination/pronation- primarily DF/PF and abd/add Navicular- highest point of medial arch Talonavicular- navicular is relatively fixed. Talus moves on fixed navicular. Maintains medial longitudinal arch. Calcaneocuboid- Rotation in transverse plane. Pulley for peroneus longus and stabilizes 1st ray. Cuboid most common foot subluxation (inferiorly).

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

Tarsometatarsal joint Connection from cuneiforms/cuboid to metatarsals Continue function of midtarsal joint Positional regulation of metatarsals/ phalanges to the weight-bearing surface Distributes body weight laterally Pronate/supinate to keep forefoot on ground

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

Metatarsophalangeal joint Metatarsal break Oblique axis for flexion/extension passing through 2nd to 5th metatarsal heads Where foot hinges as the heel raises Rigid lever during plantarflexion Supination causes rearfoot/midfoot locking Shifts body weight from medial to lateral

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

Supporting soft tissues Plantar aponeurosis Plantar arches Ligaments

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

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

Windlass effect Tension in the aponeurosis secondary to toe extension elevates the arch by acting as a pulley around which the aponeurosis is tightened. Dorsiflexion of toes forces metatarsal head into plantar flexion and brings plantar pad over head of metatarsal

Plantar arches Longitudinal arch Transverse arch Shock absorption Continuous medially and laterally Bears most weight medially Transverse arch Mobility Extends from anterior tarsals to base of metatarsals

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

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

Running gait Stance phase Swing 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 Double float Stride length Step length Cadence Velocity=stride length x cadence Double float- neither limb is in contact with the floor. Beginning and end of each running swing phase. Stride length- distance from initial contact of one foot until initial contact of contralateral foot Step length- distance from IC of one foot until IC of the same foot. One complete gait cycle. Cadence- number of steps in a given period of time. Average natural cadence- 101 to 122 steps/minute. Women- average cadence 6 to 9 steps a minute higher than men.

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

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

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?? One theory is that the decreased time in supination in running is the cause of increased injuries during running- loss of stable foot position.

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

Running gait- midtarsal joint 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

Axis of transverse tarsal joint Calcaneus in eversionparallel axes (talonavicular and calcaneocuboid). Increased motion in the transverse tarsal joint. Increased flexibility. Pronation B. Calcaneus in inversion axes are oblique Decreased motion in transverse tarsal joint. Increased stability. More rigid. Supination Page 13 O'Connor FG, Wilder RP: Textbook of Running Medicine, McGraw Hill Companies, 2001. Page 13.

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

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

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 Newton’s third law- for every action there is an equal and opposite reaction Vertical- small force peak in first 20% of stance and gradual larger peak in remainder of stance. Fore-aft- absorption and propulsion

External forces Foot strike pattern Forefoot Midfoot Rearfoot

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

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

Center of Pressure Page 17. O'Connor FG, WilderRP: Textbook of Running Medicine, McGraw-Hill Companies, 2001. Page 17

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

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

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

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

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

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

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

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

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

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

Neutral gait Level Heel Throughout Gait Cycle 90 Degree Medial Angle Throughout Gait Cycle 25% or runners

Intrinsic abnormalities Pes cavus- abnormal supination Pes Planus- abnormal pronation

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

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

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

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

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

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

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

Arch Height Will Produce Different Levels of Flexibility Normal feet: are flexible as they grip the ground and become stiff at push off Flat feet: are flexible as they grip the ground and remain flexible at push off High arched feet are inflexible and do not adjust to terrain well, but provide a good base for push off.

Running Shoe Design In an attempt to minimize injuries, running shoes need to provide: Cushioning Motion Control Support

Anatomy of the Running Shoe Uppers                                                                                                                                         Midsole Outersole Vamp- toe box (wide to prevent blisters), toe cap (protects toes and durability), throat (make sure not too tight) Quarters- conform to arch and midfoot. Stability with stabilizing bars or arch braces. Heel counter- withstand torsional force. Rear stability. Reduce speed of pronation and rotation Midsole

Anatomy of the Running Shoe Heel notch Lacing system Toebox Heel counter Outersole- traction and protection from surface. Carbon rubber- dense, durable, not flexible. Blown rubber- lighter and more flexible. OR hard rubber- mixture. Insole- reduce friction. Remove when using orthotics. Neoprene vs. viscoelastic Tongue

Anatomy of the Running Shoe Flex Grooves                                                                                                                                         Split Heel

Anatomy of the Running Shoe Last (Curvature) Straight, Semi-curved and Curved If we looked at arch only, the shoe on the left (straight) would be worn by low-arched runners: the middle (semi-curved) by normal-arched runners; and the right (curved) by high-arches runners. However, the running shoe clinic’s main diagnostic tool is dynamic assessment of your running gait. Arch shape is a secondary factor in the shoe selection process.

Anatomy of the Running Shoe Lasts (Shoe Template) Board Slip Combination If you cannot remove insole, remove shoe…it is of poor quality

Shoe Design Motion Control, Stability, Cushion Mod-Severe overpronator Stability majority of the population, slight overpronation Cushioned Neutral/underpronator runner

Stabilizing Features Support is added to the inside or medial portion of the heel to counteract the foot rolling inward (pronation)

Running Shoe Selection The three basic types of running gait based on ankle biomechanics are: over-pronation, neutral and underpronation Shoes should be bought to accommodate your running gait, not your arch height!

Shoe prescription High arch- curve-lasted, cushion shoe Flat arch- motion control or stability shoes with firm midsoles and straight to semi-curved lasts Neutral arch- cushion or stability shoe

Orthotics Effectiveness Gross, et al. 90% with symptom improvement Schere. 81% with complete symptoms relief Blake and Denton. Reduced pain associated with plantar fasciitis by 80%. American journal of Sport Medicine. 1991. 347 runners with knee, foot, ankle, and hip pain. 31% complete relief, 45% great improvement, 15% slight improvement. 90% continued to use orthotic after symptoms resolved. 90% satisfaction. Journal of American Podiatric Medical Association. 1991. Studied 43 patients with symptoms due to heel spurs. Treated with customized rigid plastic foot orthosis. 81% with complete symptom relief. JAPMA. 1985. Functional foot orthosis for plantar fasciitis. Reduced pain by 80%.

Orthotics Motion control Shock absorption Control excessive pronation Shock absorption Pressure relief in specific area Plantar heel or great toe metatarsophalangeal Redistribution of forces away from area Metatarsal pad for metatarsalgia/Morton’s neuroma

Orthotics Adjunct to rehab and training modification Return athlete to full function Prevent further injury Functional orthoses Alter foot function Guide foot through stance phase Promote biomechanical efficiency

Orthotics Start with soft temporary orthotic Over-the counter prefabricated devices Most athletes report improvement Incomplete improvementcustom orthotic                                                                

High arch orthotic Dropped forefoot Plantarflexed first metatarsal and forefoot valgus Decreased subtalar range of motion Plantarflexed first ray, unstable cuboid Peroneal cuboid syndrome

Pronated foot orthotic Flat medial arch Unstable rearfoot and excessive motion of plantar calcaneal fat pad Weak plantarflexion of first metatarsal head and weak “windlass” effect

Common mistakes Only looking at standing gait Failure to evaluate various needs of different runners Need of different orthoses for running and everyday activity

Summary Understand normal foot biomechanics- pronation vs. supination Evaluate with functional arch and shoe wear Signs of abnormal arch Match shoes and orthotics to running alignment- correct shoes and over-the-counter inserts first

Questions??