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Physiology & Rehabilitation MCQs

Practice Set 23 of 26

This practice set contains high-yield board review questions covering key concepts in Physiology & Rehabilitation. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 441

Topic: Physiology & Rehabilitation

During normal human walking, at which phase of the gait cycle does the gluteus maximus exhibit its peak muscle activity?

. Initial contact and loading response
. Mid stance
. Terminal stance
. Pre-swing
. Initial swing

Correct Answer & Explanation

. Initial contact and loading response

Explanation

The gluteus maximus acts eccentrically during initial contact and loading response to decelerate the forward momentum of the trunk and prevent excessive hip flexion. This phase represents its peak activity during the gait cycle.

Question 442

Topic: Physiology & Rehabilitation

A patient presents with a severe limp secondary to hip osteoarthritis. Gait analysis reveals that during the stance phase on the right leg, the patient significantly leans their trunk laterally over the right hip. Which biomechanical alteration primarily explains the benefit of this compensatory mechanism?

. It increases the lever arm of the abductor musculature
. It moves the center of gravity closer to the center of the hip joint, reducing the required abductor force
. It increases the joint reaction force to stabilize the hip capsule
. It shifts the ground reaction force vector anterior to the knee joint
. It actively shortens the functional leg length to improve swing clearance

Correct Answer & Explanation

. It moves the center of gravity closer to the center of the hip joint, reducing the required abductor force

Explanation

A lateral trunk lean over the affected hip (compensated Trendelenburg gait) shifts the body's center of gravity closer to the hip joint's center of rotation. This shortens the lever arm of body weight, drastically reducing the force required by the hip abductors and lowering the overall hip joint reaction force.

Question 443

Topic: Physiology & Rehabilitation

At what phases of the normal gait cycle does the vertical ground reaction force reach its two primary peaks?

. Initial contact and mid-stance
. Loading response and terminal stance
. Mid-stance and pre-swing
. Initial contact and pre-swing
. Terminal stance and initial swing

Correct Answer & Explanation

. Loading response and terminal stance

Explanation

During a normal gait cycle, the vertical ground reaction force is bimodal. It peaks at approximately 120% of body weight during loading response (weight acceptance) and again during terminal stance (push-off).

Question 444

Topic: Physiology & Rehabilitation

During normal gait, "foot slap" immediately following initial contact is clinically prevented by which of the following muscular actions?

. Concentric contraction of the gastrocnemius
. Eccentric contraction of the tibialis anterior
. Isometric contraction of the tibialis posterior
. Concentric contraction of the extensor hallucis longus
. Eccentric contraction of the soleus

Correct Answer & Explanation

. Eccentric contraction of the tibialis anterior

Explanation

From initial contact to loading response, the ankle rapidly plantarflexes. The tibialis anterior and other ankle dorsiflexors contract eccentrically to control this descent, preventing an abrupt "foot slap."

Question 445

Topic: Physiology & Rehabilitation

During normal level walking, at what phase of the gait cycle does the compressive joint reaction force at the ankle reach its maximum, and what is its approximate magnitude relative to body weight (BW)?

. Mid-stance; 1 to 2 times BW
. Terminal stance; 4 to 5 times BW
. Initial contact; 2 to 3 times BW
. Loading response; 1 to 2 times BW
. Swing phase; less than 1 time BW

Correct Answer & Explanation

. Terminal stance; 4 to 5 times BW

Explanation

The ankle joint reaction force peaks during terminal stance (heel off) due to the massive contraction of the triceps surae required for push-off. This compressive force routinely reaches 4 to 5 times body weight (and sometimes higher).

Question 446

Topic: Physiology & Rehabilitation

A patient exhibits a compensated Trendelenburg gait on the right side. During the stance phase of the right leg, which of the following kinematic adaptations is predominantly observed?

. The pelvis drops significantly on the right side
. The pelvis drops significantly on the left side
. The trunk leans laterally over the right hip
. The trunk leans laterally over the left hip
. Excessive external rotation of the right leg

Correct Answer & Explanation

. The trunk leans laterally over the right hip

Explanation

In a compensated Trendelenburg gait, the patient leans their trunk laterally over the weak stance hip (right side). This shifts the body's center of mass closer to the hip joint center, reducing the moment arm of body weight and decreasing the demand on the weak abductor muscles.

Question 447

Topic: Physiology & Rehabilitation

A patient with a 4 cm structural true limb length discrepancy (short right leg) presents for gait evaluation. Which of the following is the most common biomechanical compensation observed during the stance phase of the short (right) extremity?

. Increased right knee flexion
. Right ankle dorsiflexion
. Right ankle equinus (plantarflexion)
. Left pelvic drop
. Left trunk lean

Correct Answer & Explanation

. Right ankle equinus (plantarflexion)

Explanation

To functionally lengthen a short limb and reach the ground without dropping the pelvis excessively, patients typically adopt an equinus (plantarflexed) posture at the ankle on the shorter side during stance.

Question 448

Topic: Physiology & Rehabilitation

During the normal human gait cycle, which of the following muscles acts eccentrically during the loading response (first rocker) to control the deceleration of the foot to the ground?

. Gastrocnemius
. Soleus
. Tibialis anterior
. Gluteus maximus
. Quadriceps

Correct Answer & Explanation

. Tibialis anterior

Explanation

The tibialis anterior acts eccentrically from initial contact to foot flat (loading response) to prevent foot slap. The gastrocnemius and soleus act eccentrically later in stance (second rocker) to control tibial advancement.

Question 449

Topic: Physiology & Rehabilitation

A patient presents with a 'Trendelenburg gait' characterized by a lateral trunk lean towards the stance limb. Which of the following best describes the biomechanical rationale for this compensatory trunk shift?

. It increases the lever arm of the weak gluteus medius
. It shifts the center of gravity away from the affected hip joint
. It reduces the moment arm of the body weight relative to the hip joint center
. It creates an extensor moment at the knee to compensate for quadriceps weakness
. It maximizes the moment arm of the contralateral hip abductors

Correct Answer & Explanation

. It reduces the moment arm of the body weight relative to the hip joint center

Explanation

In a Trendelenburg gait, shifting the trunk laterally over the weak stance hip moves the body's center of gravity closer to the hip joint center. This reduces the moment arm of body weight, drastically decreasing the demand on the weak gluteus medius to maintain pelvic leveling.

Question 450

Topic: Physiology & Rehabilitation

In normal gait, what is the peak amount of knee flexion achieved during the swing phase to ensure adequate foot clearance?

. 20 degrees
. 40 degrees
. 60 degrees
. 80 degrees
. 100 degrees

Correct Answer & Explanation

. 60 degrees

Explanation

Normal human gait requires approximately 60 to 65 degrees of knee flexion during the initial and mid-swing phases to ensure adequate foot clearance. The knee then extends again in preparation for initial contact.

Question 451

Topic: Physiology & Rehabilitation

Which of the following descriptions best characterizes the 'second rocker' of the normal gait cycle?

. It occurs from initial contact to foot flat, pivoting around the heel
. It involves pivoting of the tibia over the plantigrade foot, relying on eccentric calf muscle control
. It occurs from heel off to toe off, transferring weight to the metatarsal heads
. It is the phase where the hip flexors initiate the swing phase
. It involves concentric contraction of the tibialis anterior to clear the toes

Correct Answer & Explanation

. It involves pivoting of the tibia over the plantigrade foot, relying on eccentric calf muscle control

Explanation

The second rocker (ankle rocker) occurs during mid-stance when the tibia rolls forward over the planted foot. This forward momentum is eccentrically controlled by the soleus and gastrocnemius muscles to prevent premature dorsiflexion collapse.

Question 452

Topic: Physiology & Rehabilitation

A 16-year-old female presents with bilateral in-toeing. Clinical examination reveals 80 degrees of hip internal rotation and 10 degrees of hip external rotation bilaterally. Which of the following compensatory gait abnormalities is most likely to be observed simultaneously?

. Excessive external tibial torsion
. Varus thrust at the knee
. Trendelenburg gait
. Steppage gait
. Excessive pelvic rotation during swing phase

Correct Answer & Explanation

. Excessive external tibial torsion

Explanation

The clinical examination indicates excessive femoral anteversion. These patients often develop compensatory external tibial torsion to keep the feet relatively straight during gait, leading to a complex torsional profile known as Miserable Malalignment Syndrome.

Question 453

Topic: Physiology & Rehabilitation

During the stance phase of gait, a patient exhibits a contralateral pelvic drop accompanied by a compensatory lateral trunk lean toward the stance limb. Biomechanically, what is the primary purpose of this lateral trunk lean?

. To shift the center of gravity laterally, reducing the required hip abductor force.
. To increase the moment arm of the hip abductors, generating more torque.
. To counteract a deficient gluteus maximus and prevent anterior trunk flexion.
. To prevent knee buckling secondary to quadriceps weakness.
. To increase the mechanical advantage of the ipsilateral adductor longus.

Correct Answer & Explanation

. To shift the center of gravity laterally, reducing the required hip abductor force.

Explanation

A Trendelenburg gait with a lateral trunk lean shifts the body's center of gravity closer to the center of rotation of the hip joint. This reduces the lever arm of the body weight, thereby decreasing the torque that the weakened hip abductors must counteract.

Question 454

Topic: Physiology & Rehabilitation

During the loading response phase of a normal gait cycle, where does the ground reaction force (GRF) vector pass relative to the knee joint, and which muscle group is primarily active to control this motion?

. Posterior to the knee; Quadriceps (eccentric contraction)
. Anterior to the knee; Quadriceps (concentric contraction)
. Posterior to the knee; Hamstrings (eccentric contraction)
. Anterior to the knee; Hamstrings (concentric contraction)
. Directly through the knee axis; Gastrocnemius (isometric contraction)

Correct Answer & Explanation

. Posterior to the knee; Quadriceps (eccentric contraction)

Explanation

In the loading response, the GRF vector passes posterior to the knee, creating a flexion moment. The quadriceps fire eccentrically to absorb shock and control this early knee flexion.

Question 455

Topic: Physiology & Rehabilitation

In an uncompensated Trendelenburg gait due to right gluteus medius weakness, which kinematic abnormality is observed during the stance phase of the right lower extremity?

. The pelvis drops on the right side.
. The pelvis drops on the left side.
. The trunk leans excessively to the left side.
. The right knee goes into recurvatum.
. The left hip excessively externally rotates.

Correct Answer & Explanation

. The pelvis drops on the left side.

Explanation

In an uncompensated Trendelenburg gait, weak abductors on the stance leg (right) fail to maintain a level pelvis, causing the pelvis to drop on the contralateral (left) swing side.

Question 456

Topic: Physiology & Rehabilitation

During the terminal stance phase of normal human walking, what is the primary role of the triceps surae (gastroc-soleus complex)?

. Concentric contraction to initiate early swing.
. Eccentric contraction to control tibial advancement over the planted foot.
. Concentric contraction to provide maximum push-off power.
. Eccentric contraction to decelerate knee extension.
. Isometric contraction to stabilize the subtalar joint.

Correct Answer & Explanation

. Eccentric contraction to control tibial advancement over the planted foot.

Explanation

During terminal stance, the gastroc-soleus complex primarily fires eccentrically to control the forward advancement of the tibia over the foot (controlling dorsiflexion). Peak concentric push-off power occurs slightly later in pre-swing.

Question 457

Topic: Physiology & Rehabilitation

Human gait utilizes several determinants to minimize the displacement of the center of gravity (COG), thereby reducing energy expenditure. Which of the following mechanisms is most responsible for limiting the highest vertical excursion of the COG during midstance?

. Pelvic rotation in the transverse plane
. Knee flexion during the stance phase
. Ankle plantarflexion at push-off
. Lateral displacement of the pelvis
. Arm swing during contralateral step

Correct Answer & Explanation

. Knee flexion during the stance phase

Explanation

Knee flexion during the stance phase (approximately 15 degrees) shortens the lower extremity during midstance, effectively limiting the peak vertical excursion of the center of gravity.

Question 458

Topic: Physiology & Rehabilitation

Peak knee flexion during the stance phase of normal human walking occurs at which specific event, and what is its primary function?

. Initial contact, to decelerate the forward momentum of the trunk
. Loading response, to facilitate shock absorption
. Midstance, to lower the center of gravity
. Terminal stance, to store energy for push-off
. Pre-swing, to clear the toes from the ground

Correct Answer & Explanation

. Loading response, to facilitate shock absorption

Explanation

Peak knee flexion during the stance phase (approximately 15 to 20 degrees) occurs at the end of the loading response (about 15% of the gait cycle). Its primary biomechanical function is to absorb the shock of initial ground contact.

Question 459

Topic: Physiology & Rehabilitation

During normal human walking, at which phase of the gait cycle does the ankle plantarflexor muscle group generate its maximum concentric power (often referred to as the A2 power burst)?

. Initial contact
. Loading response
. Midstance
. Terminal stance into pre-swing
. Initial swing

Correct Answer & Explanation

. Terminal stance into pre-swing

Explanation

The peak concentric power generation of the ankle plantarflexors occurs during terminal stance and transitions into pre-swing. This provides the primary propulsive force (push-off) for forward progression of the body.

Question 460

Topic: Physiology & Rehabilitation

A patient exhibits a compensated Trendelenburg gait (abductor lurch) over the right lower extremity. How is the body's center of mass shifted during the stance phase to minimize the demands on the affected right hip abductors?

. Shifted anteriorly over the right hip joint
. Shifted laterally over the left lower extremity
. Shifted laterally over the right lower extremity
. Shifted posteriorly to lock the hip joint
. Maintained centrally by decreasing the stride length

Correct Answer & Explanation

. Shifted laterally over the right lower extremity

Explanation

In a compensated Trendelenburg gait, the patient leans the trunk laterally over the weak (right) hip. This shifts the center of gravity closer to the center of rotation of the hip joint, shortening the body weight lever arm and reducing the required abductor force.

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