DPM Clinical Biomechanics 2 — Questions and Answers
Question 1: During the contact phase of gait, which muscle group acts eccentrically to control the rate of pronation?
- Tibialis anterior
- Peroneals
- Tibialis posterior (Correct answer)
- Gastrocnemius
Correct answer: Tibialis posterior
The tibialis posterior decelerates subtalar joint pronation eccentrically during the contact phase of gait.
Question 2: What is the functional significance of the angle of gait (toe-out angle) averaging approximately 7 degrees?
- It maximizes push-off power
- It aligns the foot with the line of progression to optimize lever arm efficiency (Correct answer)
- It reduces calcaneal eversion
- It prevents forefoot adduction
Correct answer: It aligns the foot with the line of progression to optimize lever arm efficiency
A 7-degree toe-out angle aligns the foot's propulsive axis with the line of progression, optimizing the lever arm for push-off.
Question 3: The windlass mechanism is most dependent on which anatomical structure becoming taut?
- Achilles tendon
- Spring ligament
- Plantar fascia (Correct answer)
- Long plantar ligament
Correct answer: Plantar fascia
Dorsiflexion of the hallux tightens the plantar fascia, elevating the medial longitudinal arch via the windlass mechanism.
Question 4: In Root's neutral position casting technique, the subtalar joint is held at what position?
- Maximum pronation
- Maximum supination
- Neutral — one-third of total range from supination (Correct answer)
- Neutral — midpoint of total frontal plane range
Correct answer: Neutral — one-third of total range from supination
Root's technique defines subtalar neutral as the position one-third of total range from full supination (or two-thirds from full pronation).
Question 5: Which forefoot deformity involves the plane of the metatarsal heads being inverted relative to the rearfoot when the subtalar joint is in neutral?
- Forefoot valgus
- Forefoot varus (Correct answer)
- Flexible forefoot valgus
- Plantarflexed first ray
Correct answer: Forefoot varus
Forefoot varus is defined as inversion of the forefoot relative to the rearfoot when the subtalar joint is in neutral position.
Question 6: During propulsion, the foot must supinate for rigid lever function. Which joint motion primarily achieves this resupination?
- Ankle dorsiflexion
- Subtalar joint inversion/supination (Correct answer)
- Midtarsal joint locking
- First MTP dorsiflexion
Correct answer: Subtalar joint inversion/supination
Subtalar joint supination locks the transverse tarsal joint, converting the foot into a rigid lever for efficient push-off.
Question 7: A patient with a rearfoot varus deformity and compensated subtalar joint will demonstrate which characteristic at the midstance phase?
- Excessive supination
- Excessive pronation as the STJ compensates (Correct answer)
- Normal arch height
- Calcaneal inversion
Correct answer: Excessive pronation as the STJ compensates
Compensated rearfoot varus causes excessive STJ pronation during midstance as the foot attempts to bring the metatarsal heads to the ground.
DPM Clinical Biomechanics 2
During the contact phase of gait, which muscle group acts eccentrically to control the rate of pronation?