Orthotic and Podiatric Biomechanics

Question 1

Orthotic device

Answer 1

added to the body part to enhance function, prevent pain, or injury

Question 2

Podiatry

Answer 2

Branch of medicine dedicated to the diagnosis, treatment, and prevention of foot and ankle disorder

Question 3

History of Podiatry: Ancient Egypt (2400 BC)

Answer 3

Earliest recorded foot treatments on tomb painting; later found in ebers papyrus

Question 4

History of Podiatry: Ancient Greece and Renaissance (500 BC - 1500 AD)

Answer 4

• Hippocrates wrote about treatment of corns
• Leonardo da Vinci’s anatomical drawings

Question 5

History of Podiatry: 19-20th century

Answer 5

• 1895-1911 first podiatry society and school opened
• Dr.william scholl popularized commercial arch supports
• Dr. Merton Root: father of podiatric biomechanics identified normal and abnormal foot function using analysis; introduced functional foot orthotic, devised a foot and lower extremity classification scheme, introduced a standardized orthosis casting method with the foot held around the subtalar joint neutral potion

Question 6

Root Theory

Answer 6

Defined neutral foot alignment as the biomechanical standard

Question 7

Inversion-eversion

Answer 7

Subtalar joint motion

Question 8

Supination-pronation

Answer 8

Motion of the ankle complex (foot relative to tibia

Question 9

Subtalar joint

Answer 9

• Very important joint within the foot for podiatrists
• Located between talus and calcaneus
• Joint axis normally directed toward the great two, can be palpated for
• deviations cause pain during walking

Question 10

Subtalar joint axis: medial deviation

Answer 10

Axis shifts inward
- flat foot, fallen arch

Question 11

Subtalar joint axis: lateral deviation

Answer 11

Axis shifts outward
- high arch, rigid foot

Question 12

Measuring STJ ROM

Answer 12

• Patient Position: Typically measured in prone position, with foot hanging freely off the edge of the table
  Measurement position
• One hand stabilizes the leg
• The other passively inverts and everts the foot to assess motion
• Place goniometer between the malleoli
• Maximally invert the STJ
• Zero goniometer then maximally evert
• Neutral position is usually found 1/3 from full inversion and 2/3 from full eversion

Question 13

Uncompensated Rearfoot Varus

Answer 13

• The calcaneus and forefoot remain inverted even when the STJ is in neutral
• The foot fails to evert fully, preventing the medial side from making proper ground contact

Question 14

Compensated Rearfoot varus

Answer 14

• The person compensates by overpronating the STJ especially during weight-bearing, allowing the medial heel to touch the ground
• This compensation can lead to instability, excessive stress on soft tissue, and overuse injuries

Question 15

Orthotic intervention for rearfoot varus

Answer 15

A medial heel wedge can be used to support the calcaneus and
help maintain STJ neutral, reducing compensatory stress.

Question 16

Uncompensated Forefoot Varus

Answer 16

• The plane of the metatarsal heads is inverted relative to the rearfoot when the subtalar joint (STJ) is neutral.
• The first metatarsal does not make contact with the ground, leading to excessive weight on the lateral forefoot.

Question 17

Compensated Forefoot Varus

Answer 17

• The person compensates by pronating the STJ during midstance and terminal stance to allow the first metatarsal to contact the ground.
• This excessive pronation may lead to joint instability, overuse injuries, and medial knee stress

Question 18

Orthotic Solution for Forefoot Varus

Answer 18

• A medial forefoot wedge can provide support the forefoot and maintain subtalar neutral.

Question 19

Uncompensated Forefoot Valgus

Answer 19

• The metatarsals are everted relative to the calcaneus when the STJ is neutral.
• This results in excessive weight distribution on the medial forefoot, potentially causing instability

Question 20

Compensated Forefoot Valgus

Answer 20

• During midstance and late stance, the STJ supinates away from neutral to adjust for the forefoot’s excessive eversion.
• This compensation can lead to lateral instability, ankle sprains, and inefficient propulsion

Question 21

Orthotic solution for forefoot valgus

Answer 21

A lateral forefoot wedge can help support the forefoot and maintain subtalar neutral

Question 22

Dynamic Rearfoot motion

Answer 22

Tracks Talus and Calcaneus Motion
* Used during weight-bearing movements like walking and running on a treadmill.

Reveals Misalignment in Motion
* Video analysis shows tibia-calcaneus misalignment throughout the stance phase.

Loaded vs. Unloaded Foot Differences
* Rearfoot motion under load can differ significantly from passive range of motion assessments.

Traditional vs. Modern Assessment
* Older method: Examining shoe wear patterns to infer foot loading.
* Modern method: Motion analysis provides real-time, precise data.

Question 23

Internal shoe wear

Answer 23

• Wear along the inside edge of the shoe, near the big toe and medial heel.
• Low arch, pronation

Question 24

Central Shoe Wear

Answer 24

Wear under big toe. Neutral foot gait naturally rests on the first toe, without excessive rotation during the stride.
- Normal arch and ankle position

Question 25

External shoe wear

Answer 25

Wear along the outer edge of the shoe, near the little toe and lateral heel. - High arch, supination

Question 26

Impact of Orthoses

Answer 26

- Orthotic may appear to correct motion, but it might only treat the symptom rather than the underlying cause - usually caused by: Muscle weakness/imbalances, flexibility deficits, leg structure

Question 27

Center of Pressure (CoP) and Ground Reaction Force (GRF)

Answer 27

CoP identifies where the GRF acts, allowing calculation of the moment about the STJ axis.

Question 28

Pronatory Effect

Answer 28

if CoP is lateral to the STJ axis, the GRF creates a pronation moment, attempting to roll the foot inward

Question 29

Supinatory Effect

Answer 29

If CoP is medial to the STJ axis, the GRF creates a supination moment, attempting to roll the foot outward.

Question 30

No Moment about the STJ

Answer 30

If CoP is directly beneath the STJ axis, there is no moment or torque, as the forces are balanced.

Question 31

Sources of moments of STJ axis

Answer 31

- Muscles create moments such as the posterior tibial (PT) muscle, which resists the pronation moment caused by the GRF - If the pronation moment is excessive, it may lead to posterior tibial tendon dysfunction - Plantar fascia action and bone-on-bone forces at the end range of motion also provide resistance to the GRF

Question 32

Reducing Moments and relieving symptoms

Answer 32

* Identifying the painful structure support orthotic design that reduce or shift stress. * Extrinsic wedges, posts, pads, cast skives, and shoe modifications can shift CoP relative to the STJ axis. * Footwear plays a crucial role in transmitting GRFs and influencing the effectiveness of foot orthotics.