DPM Clinical Biomechanics 3 — Questions and Answers
Question 1: The center of pressure (COP) during normal gait progresses from heel strike to toe-off in which general direction?
- Lateral heel → lateral midfoot → first and second metatarsals → hallux (Correct answer)
- Medial heel → medial midfoot → third metatarsal → fifth toe
- Central heel → medial arch → first metatarsal → hallux
- Lateral heel → central metatarsals → hallux
Correct answer: Lateral heel → lateral midfoot → first and second metatarsals → hallux
Normal COP progression travels from the lateral heel, across the lateral midfoot, to the first and second metatarsophalangeal region, and exits at the hallux.
Question 2: Which axis of the subtalar joint is most accurately described?
- Perpendicular to the sagittal plane
- 42 degrees from the horizontal and 16 degrees from the sagittal plane (Correct answer)
- Parallel to the long axis of the foot
- Perpendicular to the frontal plane
Correct answer: 42 degrees from the horizontal and 16 degrees from the sagittal plane
The subtalar joint axis averages 42 degrees of inclination from the horizontal plane and 16 degrees medial deviation from the sagittal plane.
Question 3: A plantarflexed first ray deformity most commonly causes which compensatory mechanism during gait?
- Supination of the subtalar joint
- Pronation of the subtalar joint to unload the first ray (Correct answer)
- Increased ankle dorsiflexion
- Toe walking
Correct answer: Pronation of the subtalar joint to unload the first ray
A plantarflexed first ray causes ground reactive force to drive the first metatarsal up, requiring the STJ to pronate to redistribute load.
Question 4: What does the term 'maximum midtarsal joint pronation' refer to in functional foot orthotic theory?
- The position where the midtarsal joint is most rigid
- The position where both midtarsal joint axes allow maximum motion simultaneously (Correct answer)
- The position of the foot at heel strike
- The point of maximum arch collapse
Correct answer: The position where both midtarsal joint axes allow maximum motion simultaneously
Maximum midtarsal joint pronation occurs when both the longitudinal and oblique axes of the midtarsal joint are parallel, allowing maximum combined motion.
Question 5: According to Kirby's subtalar joint axis location and rotational equilibrium theory, a laterally deviated STJ axis predisposes to which condition?
- Peroneal tendinopathy and supination instability (Correct answer)
- Hallux valgus and medial column overload
- Plantar fasciitis from excessive pronation
- Achilles insertional tendinopathy
Correct answer: Peroneal tendinopathy and supination instability
A laterally deviated STJ axis increases the supination moment arm of the peroneal tendons, predisposing to lateral instability and peroneal overload.
Question 6: Ground reaction force (GRF) during normal walking shows a characteristic double-peak pattern in the vertical component. What do the two peaks represent?
- Heel contact and toe-off loading events
- The body's weight bearing during deceleration and acceleration phases (Correct answer)
- Eccentric and concentric muscle activity peaks
- Medial and lateral column loading
Correct answer: The body's weight bearing during deceleration and acceleration phases
The first vertical GRF peak represents the loading response (deceleration), and the second peak represents propulsive loading during terminal stance.
Question 7: The 'negative windlass' or 'reverse windlass' concept describes what phenomenon?
- Plantar fascia laxity during pronation that flattens the arch
- Plantar fascia tightening during hallux plantarflexion that depresses the arch (Correct answer)
- Dorsiflexion resistance from the plantar fascia
- Achilles-plantar fascia coupling
Correct answer: Plantar fascia tightening during hallux plantarflexion that depresses the arch
The reverse windlass describes how plantarflexion of the hallux releases tension on the plantar fascia, allowing the arch to drop.
DPM Clinical Biomechanics 3
The center of pressure (COP) during normal gait progresses from heel strike to toe-off in which general direction?