APMLE APMLE Biomechanics and Orthopedics 1 — Questions and Answers
Question 1: Which term describes the triplanar motion of the subtalar joint that includes dorsiflexion, abduction, and eversion?
- Pronation (Correct answer)
- Supination
- Plantarflexion
- Adduction
Correct answer: Pronation
Pronation of the subtalar joint is a triplanar motion combining dorsiflexion, abduction, and eversion.
Question 2: What is the normal range of motion for subtalar joint pronation to supination?
- 2:1 ratio of supination to pronation (Correct answer)
- 1:1 ratio
- 1:2 ratio of supination to pronation
- 3:1 ratio of pronation to supination
Correct answer: 2:1 ratio of supination to pronation
The normal subtalar joint has a 2:1 ratio of supination to pronation range of motion.
Question 3: Which axis of the subtalar joint is responsible for its triplanar motion?
- Oblique axis oriented 42° from transverse and 16° from sagittal plane (Correct answer)
- Vertical axis perpendicular to the ground
- Horizontal axis parallel to the floor
- Axis oriented 90° to the long axis of the foot
Correct answer: Oblique axis oriented 42° from transverse and 16° from sagittal plane
The subtalar joint axis is oblique, oriented approximately 42° from the transverse plane and 16° from the sagittal plane.
Question 4: What is the term for the period of gait when both feet are in contact with the ground simultaneously?
- Double support (Correct answer)
- Single limb support
- Swing phase
- Terminal stance
Correct answer: Double support
Double support refers to the brief period in normal gait when both feet are simultaneously in contact with the ground.
Question 5: A patient presents with a forefoot varus deformity. Which compensation occurs at the subtalar joint during gait?
- Subtalar joint pronation (Correct answer)
- Subtalar joint supination
- Midtarsal joint locking
- Ankle plantarflexion
Correct answer: Subtalar joint pronation
Forefoot varus causes the subtalar joint to pronate to allow the medial forefoot to contact the ground.
Question 6: Which muscle is the primary invertor of the foot and is commonly tested when evaluating posterior tibial tendon dysfunction?
- Tibialis posterior (Correct answer)
- Tibialis anterior
- Peroneus longus
- Flexor digitorum longus
Correct answer: Tibialis posterior
The tibialis posterior is the primary invertor of the foot and its dysfunction leads to adult-acquired flatfoot deformity.
APMLE APMLE Biomechanics and Orthopedics 1
Which term describes the triplanar motion of the subtalar joint that includes dorsiflexion, abduction, and eversion?