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Physiology & Rehabilitation MCQs

Practice Set 4 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 61

Topic: Physiology & Rehabilitation

A 70-year-old patient with a history of stroke presents with a dynamic genu recurvatum during the stance phase of gait. Unlike patients with purely osseous recurvatum, this patient exhibits a marked hyperextension thrust that worsens with fatigue. The text highlights that the deceptively normal gait seen in compensated osseous recurvatum 'shatters completely when muscle weakness is introduced into the equation.' What is the most likely reason for the breakdown of compensated gait in the presence of muscle weakness in a patient with underlying osseous recurvatum?

. Muscle weakness directly causes the osseous deformity to worsen over time.
. The weakened muscles are unable to provide the active, dynamic control needed to prevent the knee from snapping into full passive hyperextension.
. Muscle weakness leads to increased ligamentous laxity, which then causes the recurvatum.
. The body compensates by increasing ankle dorsiflexion, which exacerbates knee recurvatum.
. Muscle weakness primarily affects the swing phase, leading to toe drag rather than stance phase instability.

Correct Answer & Explanation

. The weakened muscles are unable to provide the active, dynamic control needed to prevent the knee from snapping into full passive hyperextension.

Explanation

Correct Answer: BThe text states, 'The deceptively normal gait pattern seen in compensated osseous recurvatum shatters completely when muscle weakness is introduced into the equation. The anteroposterior stability of the knee during the stance phase is an active, dynamic process controlled by the delicate balance between the quadriceps and [hamstrings].' In the presence of muscle weakness (e.g., hamstrings or quadriceps imbalance), the patient loses the ability to actively control the knee's position, allowing the underlying bony recurvatum to manifest as a dynamic hyperextension thrust during weight-bearing.Option A is incorrect; muscle weakness does not directly alter bone shape or worsen an existing osseous deformity.Option C is incorrect; muscle weakness does not cause ligamentous laxity. Ligamentous laxity is a separate etiology for recurvatum.Option D is incorrect; the primary compensation for osseous recurvatum is ankle plantar flexion, not dorsiflexion. Increased dorsiflexion would further destabilize a recurvatum knee.Option E is incorrect; while muscle weakness can affect the swing phase, the question specifically addresses the breakdown of compensated gait during thestance phasedue to recurvatum, which is a stability issue.

Question 62

Topic: Physiology & Rehabilitation

A 62-year-old male presents with chronic knee pain and difficulty with ambulation, noting significant fatigue after short distances. Clinical examination reveals a fixed knee flexion deformity (FFD) of 15 degrees. During the mid-stance phase of gait, which of the following biomechanical alterations is most characteristic of this patient's condition?

. The Ground Reaction Vector (GRV) passes anterior to the knee's center of rotation, creating an extension moment.
. The quadriceps muscle group remains largely inactive, relying on passive knee stability.
. The GRV passes posterior to the knee's center of rotation, necessitating persistent quadriceps contraction.
. The ankle joint is forced into plantarflexion to maintain a plantigrade foot.
. The hip joint primarily compensates by moving into increased extension to shift the center of mass posteriorly.

Correct Answer & Explanation

. The GRV passes posterior to the knee's center of rotation, necessitating persistent quadriceps contraction.

Explanation

Correct Answer: CThe case explicitly states that in the presence of a Fixed Flexion Deformity (FFD), the Ground Reaction Vector (GRV) is forced to passposteriorto the knee's center of rotation. This posterior shift instantly creates a powerful, pathological flexion moment that attempts to buckle the knee with every step. To prevent collapse, the patient must engage in persistent, active, isometric quadriceps contraction throughout the entire stance phase. The image provided illustrates this exact scenario, showing the GRV (yellow/green line) passing posterior to the knee's center of rotation (blue dot), creating a flexion moment.Option A is incorrectbecause this describes the normal, energy-efficient gait where the GRV passes anterior to the knee, creating a passive extension moment. This is disrupted in FFD.Option B is incorrectbecause, as explained, the posterior GRV in FFD necessitates constant, active quadriceps contraction, leading to significant energy expenditure and fatigue, directly contradicting the idea of passive stability.Option D is incorrect. For a mild FFD (5-15 degrees), the body attempts to keep the foot plantigrade by compensating withincreased ankle dorsiflexion, not plantarflexion. Plantarflexion would exacerbate the toe-walking tendency.Option E is incorrect. While the hip does compensate, it does so by moving intoincreased flexion(proximal compensation) and a slight anterior lean of the trunk, not extension. This attempts to shift the body's center of mass forward to reduce the flexion moment at the knee.

Question 63

Topic: Physiology & Rehabilitation

During a normal gait cycle, maximum knee flexion is critical to allow for adequate foot clearance. This maximum degree of knee flexion typically occurs during which phase of the gait cycle?

. Initial contact
. Mid-stance
. Terminal stance
. Initial swing
. Mid-swing

Correct Answer & Explanation

. Initial swing

Explanation

Maximum knee flexion during normal walking reaches approximately 60 degrees and occurs during the initial swing phase. This motion is essential for clearing the foot off the ground as the limb advances.

Question 64

Topic: Physiology & Rehabilitation

A 12-year-old patient with severe external tibial torsion demonstrates 'lever arm dysfunction' during clinical gait analysis. This rotational malalignment primarily impairs the biomechanical efficiency of which muscle group during the terminal stance phase?

. Quadriceps
. Hamstrings
. Gluteus medius
. Triceps surae
. Tibialis anterior

Correct Answer & Explanation

. Triceps surae

Explanation

External tibial torsion outwardly rotates the foot progression angle, shortening the effective sagittal lever arm of the foot. This significantly reduces the push-off power generated by the triceps surae (gastrocnemius-soleus complex) during terminal stance.

Question 65

Topic: Physiology & Rehabilitation

A patient with advanced osteoarthritis of the right hip presents with a compensated Trendelenburg gait. Which kinematic alteration best describes how this patient minimizes the required abductor force during the stance phase on the affected leg?

. Leaning the trunk away from the right hip.
. Leaning the trunk laterally over the right hip.
. Increasing lumbar lordosis dramatically.
. Flexing the trunk forward over the knee.
. Circumducting the right leg during swing.

Correct Answer & Explanation

. Leaning the trunk laterally over the right hip.

Explanation

In a compensated Trendelenburg gait (abductor lurch), the patient shifts their trunk laterally over the affected hip. This moves the center of gravity closer to the joint center, drastically reducing the moment arm of body weight and decreasing the force required by the weak abductors.

Question 66

Topic: Physiology & Rehabilitation

Saunders et al. described six classic 'determinants of gait' designed to minimize the vertical and lateral displacement of the body's center of gravity. Which determinant is primarily responsible for lowering the highest point (apex) of the center of gravity trajectory during the stance phase?

. Pelvic rotation
. Pelvic tilt
. Knee flexion in stance
. Foot and ankle mechanisms
. Lateral displacement of the pelvis

Correct Answer & Explanation

. Knee flexion in stance

Explanation

Knee flexion during the stance phase (typically around 15 degrees) serves to lower the body's center of gravity at the peak of its trajectory, thereby flattening the arc of motion and conserving energy.

Question 67

Topic: Physiology & Rehabilitation

During normal human gait, maximum ankle dorsiflexion typically occurs during which specific phase of the gait cycle?

. Loading response
. Mid-stance
. Terminal stance
. Pre-swing
. Initial swing

Correct Answer & Explanation

. Terminal stance

Explanation

Maximum ankle dorsiflexion of approximately 10 degrees occurs at the end of terminal stance. This occurs just before the heel lifts off the ground and weight transfers to the contralateral limb.

Question 68

Topic: Physiology & Rehabilitation

During a formal gait analysis, a patient demonstrates excessive knee flexion and delayed heel off during the terminal stance phase of the gait cycle. Weakness in which of the following muscle groups is the most likely biomechanical cause of this abnormal gait pattern?

. Hip flexors
. Hip extensors
. Knee extensors
. Ankle dorsiflexors
. Ankle plantarflexors

Correct Answer & Explanation

. Ankle plantarflexors

Explanation

The ankle plantarflexors (gastrocnemius-soleus complex) act eccentrically during terminal stance to control the forward progression of the tibia over the foot. Weakness of this complex leads to excessive anterior tibial advancement, resulting in excessive knee flexion and a delayed heel-off.

Question 69

Topic: Physiology & Rehabilitation

During the loading response phase of normal human gait, the knee undergoes approximately 15 degrees of flexion. Which of the following best describes the primary muscle activity controlling this specific motion?

. Concentric contraction of the quadriceps
. Eccentric contraction of the quadriceps
. Concentric contraction of the hamstrings
. Eccentric contraction of the hamstrings
. Isometric contraction of the gastrocnemius

Correct Answer & Explanation

. Eccentric contraction of the quadriceps

Explanation

During the loading response phase, the knee flexes to absorb shock and accept weight. The quadriceps muscle group contracts eccentrically to control this knee flexion and prevent the knee from buckling under the body's weight.

Question 70

Topic: Physiology & Rehabilitation

In a normal gait cycle, the vertical ground reaction force (GRF) curve demonstrates a distinct bimodal (two-peak) shape. The first peak occurs during early stance and the second during late stance. What biomechanical event is primarily responsible for the measured trough (valley) between these two peaks?

. Upward vertical acceleration of the body's center of mass
. Downward vertical acceleration of the body's center of mass
. Eccentric contraction of the anterior tibialis
. Contralateral heel strike impact
. Concentric contraction of the hamstrings

Correct Answer & Explanation

. Downward vertical acceleration of the body's center of mass

Explanation

The 'valley' in the bimodal vertical ground reaction force curve occurs during midstance. As the body's center of mass rides over the stance limb like an inverted pendulum, its downward vertical acceleration results in a measured force on the force plate that is momentarily less than total body weight.

Question 71

Topic: Physiology & Rehabilitation

A patient with a distal femoral extension deformity (Mechanical Posterior Distal Femoral Angle (mPDFA) = 90°, Mechanical Posterior Proximal Tibial Angle (mPPTA) = 81°) undergoes a proximal tibial flexion osteotomy to correct their clinical hyperextension.

. Iatrogenic posterior knee subluxation
. Iatrogenic anterior knee subluxation
. Patella alta
. Accelerated patellofemoral arthritis
. Non-union of the tibial osteotomy

Correct Answer & Explanation

. Iatrogenic anterior knee subluxation

Explanation

Correct Answer: BThe case content provides a direct warning against this specific surgical error: 'Correcting Femoral Recurvatum in the Tibia (THE WRONG WAY).' The problem is a distal femoral extension deformity (mPDFA > 85°), meaning the femur is the source. The mistake is performing a flexion osteotomy of the proximal tibia to compensate. The result is that 'The tibial plateau now has an excessively increased posterior slope. The abnormally extended femoral condyles will drive the tibia violently forward during the stance phase, creating a severeiatrogenic anterior knee subluxationand placing immense, tearing strain on the PCL.'Option A is incorrect; posterior subluxation occurs when tibial recurvatum is corrected in the femur. Option C (patella alta) is a pre-existing condition or can be caused by certain osteotomy designs, but not the primary biomechanical consequence of this specific error. Option D is a long-term consequence of instability but not the immediate biomechanical complication. Option E is a general surgical complication but not the specific iatrogenic subluxation described.

Question 72

Topic: Physiology & Rehabilitation

A 62-year-old patient presents with a chronic, progressive crouched gait and significant anterior knee pain, particularly with ambulation. Clinical examination reveals a fixed flexion deformity (FFD) of the knee. The patient reports rapid quadriceps fatigue even with short distances. Based on the biomechanical principles outlined in the case, which of the following is the MOST accurate explanation for the patient's symptoms?

. The FFD leads to continuous hamstring contraction, causing posterior knee pain and limiting extension.
. The FFD results in increased patellar tendon tension, leading to patellar subluxation and instability.
. The inability to achieve full extension forces continuous quadriceps activity during stance, leading to fatigue and increased patellofemoral loads.
. The crouched gait primarily shifts the center of gravity posteriorly, reducing anterior knee pain but increasing hip and back strain.
. The FFD causes a compensatory increase in gastrocnemius strength, which exacerbates the flexion moment at the knee.

Correct Answer & Explanation

. The inability to achieve full extension forces continuous quadriceps activity during stance, leading to fatigue and increased patellofemoral loads.

Explanation

Correct Answer: CThe case explicitly states that when the knee cannot fully extend, the quadriceps mechanism is forced to fire continuously throughout the stance phase. This constant, unrelenting isometric contraction is metabolically demanding, leading to rapid muscle fatigue. Furthermore, this continuous quadriceps activity subjects the patellofemoral joint to massive, abnormal compressive loads, rapidly leading to chondromalacia, severe pain, and early-onset osteoarthritis (anterior knee pain). The crouched gait is a compensatory mechanism, not a primary cause of reduced anterior knee pain.Option A is incorrect because while hamstrings can contribute to FFD, the primary biomechanical consequence described for fatigue and anterior knee pain relates to the quadriceps. Option B is incorrect; increased patellar tendon tension is a consequence of quadriceps overactivity, but patellar subluxation is not the primary or most direct biomechanical consequence described. Option D is incorrect as the crouched gait alters the center of gravity and places immense strain on the hips and lower back, but it does not reduce anterior knee pain; rather, it's a compensatory mechanism for the knee's inability to extend. Option E is incorrect; while the gastrocnemius can contribute to soft tissue contracture, the primary mechanism for fatigue and anterior knee pain is the quadriceps' continuous firing.

Question 73

Topic: Physiology & Rehabilitation

A 45-year-old patient exhibits a unilateral fixed equinus contracture of the ankle. What is the classic compensatory sagittal plane deformity observed at the ipsilateral knee during the stance phase of gait?

. Knee flexion contracture
. Knee recurvatum (hyperextension)
. Varus thrust
. Valgus collapse
. Patellar subluxation

Correct Answer & Explanation

. Knee recurvatum (hyperextension)

Explanation

To maintain a plantigrade foot during the stance phase of gait in the presence of a fixed ankle equinus contracture, the knee must hyperextend, leading to a compensatory knee recurvatum deformity.

Question 74

Topic: Physiology & Rehabilitation

Following a successful double-level Pelvic Support Osteotomy, a patient is undergoing rehabilitation. Which of the following kinematic changes would be an expected and desirable outcome of the procedure?

. Increased hip adduction range of motion.
. Persistent lumbar hyperlordosis.
. Decreased functional hip abduction range of motion.
. Elimination of the Trendelenburg gait and correction of lumbar hyperlordosis.
. Increased hip flexion range of motion.

Correct Answer & Explanation

. Elimination of the Trendelenburg gait and correction of lumbar hyperlordosis.

Explanation

Correct Answer: DThe case outlines the 'Expected Kinematic Changes Post-Reconstruction.' It states that a correctly executed double-level PSO 'Eliminates the Trendelenburg gait entirely' and 'Corrects lumbar hyperlordosis by eliminating the fixed flexion deformity of the hip.' Regarding range of motion, it notes that 'functional hip abduction range is significantly increased, while the adduction range is decreased' and 'hip flexion is slightly decreased, while hip extension is functionally increased.' Therefore, options A, B, C, and E describe outcomes that are either incorrect or undesirable.

Question 75

Topic: Physiology & Rehabilitation

In a Paley double-level pelvic support osteotomy (PSO), what is the primary biomechanical rationale for incorporating the second, more distal osteotomy?

. Correcting residual Trendelenburg gait by tensioning the abductors
. Compensating for the extreme valgus mechanical axis deviation at the knee
. Improving a residual hip flexion contracture
. Providing a proximal fulcrum against the ilium
. Restoring the true anatomic center of rotation of the native hip

Correct Answer & Explanation

. Compensating for the extreme valgus mechanical axis deviation at the knee

Explanation

The proximal valgus osteotomy creates pelvic support but severely shifts the mechanical axis laterally, causing valgus overload at the knee. The distal varus osteotomy realigns the mechanical axis and allows for simultaneous limb lengthening.

Question 76

Topic: Physiology & Rehabilitation

A 12-year-old with untreated developmental dysplasia of the hip presents with a high dislocation and severe limp. If a pelvic support osteotomy is planned, what specific preoperative radiographic measurement determines the exact magnitude of valgus correction required at the proximal osteotomy?

. Neck-shaft angle of the dislocated proximal femur
. Center-edge angle of Wiberg
. Maximum passive adduction angle of the femur on AP pelvis radiograph
. Mechanical lateral distal femoral angle (mLDFA)
. Acetabular index

Correct Answer & Explanation

. Maximum passive adduction angle of the femur on AP pelvis radiograph

Explanation

The required degree of valgus is calculated by taking the maximum adduction angle of the femur and adding an overcorrection (typically 15 degrees). This ensures the newly created proximal femoral angle maintains contact with the ischium during stance phase.

Question 77

Topic: Physiology & Rehabilitation

A 28-year-old patient with a chronically dislocated hip from childhood sepsis undergoes a Paley double-level pelvic support osteotomy. The proximal osteotomy is designed to provide pelvic support. What is the primary biomechanical purpose of the distal osteotomy?

. To improve hip flexion and extension
. To restore the mechanical axis and allow for simultaneous limb lengthening
. To provide a broad surface for ischial impingement
. To lateralize the femoral shaft
. To correct excessive femoral version

Correct Answer & Explanation

. To restore the mechanical axis and allow for simultaneous limb lengthening

Explanation

The proximal osteotomy in a PSO creates significant valgus to support the pelvis and eliminate the Trendelenburg gait. The distal osteotomy corrects the resulting valgus mechanical axis deviation, restores parallel knee joint orientation, and serves as the site for limb lengthening.

Question 78

Topic: Physiology & Rehabilitation

When planning the proximal osteotomy in a Paley pelvic support osteotomy, the required angle of valgus correction is calculated based on preoperative radiographs. Which of the following formulas correctly determines the angle of the proximal osteotomy?

. Maximum hip abduction angle plus 15 degrees
. Maximum hip adduction angle plus 15 degrees
. Angle of mechanical axis deviation minus 10 degrees
. Maximum hip adduction angle minus 15 degrees
. Anatomic axis of the femur plus 10 degrees

Correct Answer & Explanation

. Maximum hip adduction angle plus 15 degrees

Explanation

The proximal osteotomy angle must equal the maximum adduction angle of the hip plus an additional 15 degrees of overcorrection. This overcorrection ensures the proximal femur adequately abuts the pelvis during weight-bearing, functionally eliminating the Trendelenburg gait.

Question 79

Topic: Physiology & Rehabilitation

After a successful double-level Pelvic Support Osteotomy, the patient's Trendelenburg lurch is resolved. Which structure serves as the primary fulcrum stabilizing the pelvis during the single-leg stance phase on the operative side?

. The greater trochanter abutting the ilium
. The lesser trochanter or proximal femur abutting the ischium
. The tightened gluteus medius muscle
. The tightened iliotibial band
. The psoas tendon abutting the superior pubic ramus

Correct Answer & Explanation

. The lesser trochanter or proximal femur abutting the ischium

Explanation

In a PSO, the proximal osteotomy is placed at the level of the ischial tuberosity. During weight-bearing, the proximal segment abuts the ischium, creating a mechanical fulcrum that provides pelvic support and prevents pelvic drop.

Question 80

Topic: Physiology & Rehabilitation

In an Ilizarov hip reconstruction (double-level pelvic support osteotomy) for a chronically dislocated hip, what is the primary biomechanical objective of the proximal valgus osteotomy?

. To equalize leg length discrepancy by translating the femoral shaft distally.
. To shift the mechanical axis medially to unload the lateral compartment of the knee.
. To create a bony fulcrum against the pelvis, restoring a stable fulcrum for the abductor mechanism and eliminating Trendelenburg gait.
. To realign the knee joint line parallel to the ground.
. To increase the anatomic lever arm of the gluteus maximus.

Correct Answer & Explanation

. To create a bony fulcrum against the pelvis, restoring a stable fulcrum for the abductor mechanism and eliminating Trendelenburg gait.

Explanation

The proximal valgus osteotomy abuts the ischium during weight-bearing. This creates a new fulcrum that stabilizes the pelvis, effectively substituting for the absent or dislocated femoral head and eliminating the Trendelenburg gait.

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