OCS OCS Biomechanics & Kinesiology 2 — Questions and Answers
Question 1: The convex-concave rule states that when a convex surface moves on a fixed concave surface, joint glide occurs in which direction relative to bone movement?
- Opposite direction (Correct answer)
- Same direction
- Perpendicular to bone movement
- No glide occurs
Correct answer: Opposite direction
When a convex surface moves on a concave surface, the joint glide (slide) occurs in the opposite direction of the bone's angular movement.
Question 2: During the running gait cycle, which phase is absent compared to walking gait?
- Double support phase (Correct answer)
- Loading response
- Mid-stance
- Terminal stance
Correct answer: Double support phase
Running eliminates the double support phase seen in walking and replaces it with a float phase where neither foot is in contact with the ground.
Question 3: The center of gravity in a standing adult is located approximately at which spinal level?
- S2 (Correct answer)
- L4-L5
- L2-L3
- T12-L1
Correct answer: S2
The center of gravity in a standing adult is located approximately anterior to the second sacral vertebra (S2).
Question 4: Which type of muscle contraction produces the greatest tension per cross-sectional area?
- Eccentric (Correct answer)
- Isometric
- Concentric
- Isotonic
Correct answer: Eccentric
Eccentric contractions produce greater tension than isometric or concentric contractions because cross-bridge cycling is supplemented by passive elastic forces in titin.
Question 5: The subtalar joint axis of motion is oriented at approximately 42° in the sagittal plane and 16° in the transverse plane; this orientation means subtalar pronation is a triplanar motion combining:
- Eversion, dorsiflexion, and abduction (Correct answer)
- Inversion, plantarflexion, and adduction
- Eversion, plantarflexion, and adduction
- Inversion, dorsiflexion, and abduction
Correct answer: Eversion, dorsiflexion, and abduction
Subtalar pronation is a triplanar motion consisting of calcaneal eversion, talar dorsiflexion, and forefoot abduction occurring simultaneously.
Question 6: The instantaneous axis of rotation (IAR) of the knee joint during flexion-extension moves in what pattern?
- Posteriorly during flexion (Correct answer)
- Anteriorly during flexion
- Remains fixed throughout range
- Moves superiorly during flexion
Correct answer: Posteriorly during flexion
During knee flexion, the IAR moves posteriorly due to the combination of rolling and gliding of the femoral condyles on the tibial plateau.
OCS OCS Biomechanics & Kinesiology 2
The convex-concave rule states that when a convex surface moves on a fixed concave surface, joint glide occurs in which direction relative to bone movement?