Menu

Physiology & Rehabilitation MCQs

Practice Set 5 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 81

Topic: Physiology & Rehabilitation

A 19-year-old female undergoes a double-level pelvic support osteotomy for a chronically dislocated hip. To achieve optimal mechanical support and prevent proximal femur migration, the proximal valgus osteotomy should be performed at which anatomical level?

. Subtrochanteric level, 5 cm below the lesser trochanter.
. At the level of the ischial tuberosity with the hip in maximum adduction.
. At the intertrochanteric line.
. At the mid-diaphysis.
. At the level of the greater trochanter.

Correct Answer & Explanation

. At the level of the ischial tuberosity with the hip in maximum adduction.

Explanation

In a pelvic support osteotomy, the proximal valgus osteotomy must be at the level of the ischial tuberosity during maximum adduction. This allows the proximal femur to rest against the pelvis, restoring the fulcrum and eliminating the Trendelenburg gait.

Question 82

Topic: Physiology & Rehabilitation

A patient undergoes a pelvic support osteotomy for a chronically dislocated, painful hip. Postoperatively, the patient continues to exhibit a severe Trendelenburg gait and complains of persistent pelvic drop. Which of the following technical errors most likely occurred?

. The distal osteotomy was lengthened too rapidly.
. Insufficient valgus angulation was achieved at the proximal osteotomy.
. The proximal osteotomy was placed exactly at the level of the ischial tuberosity.
. The distal osteotomy was overcorrected into varus.
. Failure to release the iliopsoas tendon.

Correct Answer & Explanation

. Insufficient valgus angulation was achieved at the proximal osteotomy.

Explanation

If insufficient valgus is achieved at the proximal osteotomy site, the femur will fail to adequately support the pelvis (ischium). This lack of a stable fulcrum leads to persistent pelvic drop and a continuing Trendelenburg gait.

Question 83

Topic: Physiology & Rehabilitation

A 68-year-old patient with long-standing bilateral knee osteoarthritis and significant varus deformities presents with difficulty ambulating and a characteristic 'waddling' gait. The clinical image below shows the patient's stance. This gait pattern is most likely a compensatory mechanism for which of the following?

. Increased quadriceps strength to overcome knee instability.
. Reduced hip abductor moment arm due to lateral shift of the trunk.
. Medial shift of the center of gravity to reduce load on the lateral compartment.
. Attempt to shift the mechanical axis laterally to offload the medial compartment.
. Increased ankle dorsiflexion to maintain foot clearance during swing phase.

Correct Answer & Explanation

. Attempt to shift the mechanical axis laterally to offload the medial compartment.

Explanation

Correct Answer: DThe image and description point to a patient with significant varus deformities and a 'waddling' gait. In a varus deformity, the mechanical axis passes medial to the knee, leading to increased compressive forces on the medial compartment. To alleviate this pain and reduce the medial compartment load, patients often adopt a compensatory gait pattern where they lean their trunk towards the affected side during stance phase. This lateral shift of the trunk effectively shifts the body's center of gravity laterally, thereby moving the mechanical axis of the limb more laterally relative to the knee joint. This maneuver aims to offload the painful medial compartment. Option A is incorrect as the gait is compensatory for pain/malalignment, not necessarily increased strength. Option B describes a consequence of the lateral shift (reduced abductor moment arm) but not the primary goal of the compensation. Option C is incorrect; the goal is to shift the center of gravitylaterallyto offload themedialcompartment. Option E relates to foot clearance, which is a different aspect of gait and not directly related to compensating for varus knee pain.

Question 84

Topic: Physiology & Rehabilitation

A 30-year-old athlete presents with a history of chronic knee pain and a subtle gait abnormality. On physical examination, the knee appears to 'lock' securely in full extension during the stance phase of gait without significant quadriceps effort. Based on the principles outlined in the case, which of the following best describes the normal sagittal mechanical axis alignment at the knee joint that facilitates this efficient gait?

. The mechanical axis passes directly through the center of the knee joint.
. The mechanical axis passes slightly posterior to the center of the knee joint, creating a passive flexion moment.
. The mechanical axis passes slightly anterior to the center of the knee joint, creating a passive extension moment.
. The mechanical axis passes through the posterior third of the tibial plateau, ensuring stability.
. The mechanical axis is highly variable at the knee joint, depending on individual anatomy.

Correct Answer & Explanation

. The mechanical axis passes slightly anterior to the center of the knee joint, creating a passive extension moment.

Explanation

Correct Answer: CThe case explicitly states: 'This mechanical line, originating from the body's center of gravity, passes through the center of the femoral head, drops slightlyanteriorto the center of the knee joint, and continues through the center of the ankle joint. This slight anterior positioning at the knee is a biomechanical masterpiece: it creates a natural, passive extension moment. This allows the knee to 'lock' securely in full extension during the stance phase of the gait cycle, requiring minimal active quadriceps effort to maintain an upright posture.'Option A is incorrectbecause while it's close, the normal axis isslightlyanterior, which is critical for the passive extension moment.Option B is incorrectbecause passing posterior would create a flexion moment, requiringmorequadriceps effort, which is characteristic of procurvatum, not normal alignment.Option D is incorrectas the description of the mechanical axis passing through the posterior third of the tibial plateau is not the standard definition of the sagittal mechanical axis at the knee joint.Option E is incorrectas while there's some individual variation, the fundamental principle of the mechanical axis passing slightly anterior to the knee for a passive extension moment is a consistent biomechanical truth for normal alignment.

Question 85

Topic: Physiology & Rehabilitation

A 40-year-old patient with a history of femoral procurvatum is being evaluated for surgical correction. The surgeon is concerned about potential postoperative hyperextension. The provided case highlights the 'neuromuscular feedback loop' and the role of dynamic restraints. Which of the following statements accurately describes the primary mechanism by which the hamstrings prevent pathologic hyperextension in a neuromuscularly intact patient?

. They act as static restraints, providing rigid stability at the end range of motion.
. They passively shorten after an extension osteotomy, mechanically blocking hyperextension.
. They serve as a 'dynamic checkrein,' receiving efferent signals from the CNS to prevent hyperextension.
. They primarily provide anterior stability to the tibia, preventing posterior subluxation.
. They stretch over time in response to procurvatum, leading to compensatory hyperextension.

Correct Answer & Explanation

. They serve as a 'dynamic checkrein,' receiving efferent signals from the CNS to prevent hyperextension.

Explanation

Correct Answer: CThe case states: 'Proprioceptive mechanoreceptors within the joint capsule, ligaments, and tendons send continuous afferent signals to the central nervous system (CNS). The CNS, in turn, fires efferent signals to the hamstrings, commanding them to act as a 'dynamic checkrein.' This prevents pathologic hyperextension during the swing and stance phases.' This describes the active, neurologically controlled role of the hamstrings.Option A is incorrectbecause the case differentiates static restraints (capsule, ligaments) from dynamic restraints (musculature like hamstrings).Option B is incorrectbecause while an extension osteotomy does relatively shorten posterior soft tissues, the primary mechanism for preventingpathologichyperextension in a neuromuscularly intact patient is the active, dynamic control by the hamstrings, not just passive mechanical shortening.Option D is incorrectbecause the hamstrings primarily provide posterior stability to the knee and act as knee flexors, not anterior stability to the tibia in the context of preventing hyperextension.Option E is incorrectbecause while the posterior capsulestretchesin response to chronic procurvatum, the hamstrings' role is topreventpathologic hyperextension through active contraction, not to stretch and cause it.

Question 86

Topic: Physiology & Rehabilitation

A 28-year-old patient with a history of poliomyelitis presents with a 35-degree femoral procurvatum and a clinical fixed flexion deformity (FFD) of 20 degrees, indicating 15 degrees of compensatory hyperextension. The patient has significant hamstring weakness and atrophy. The surgeon is planning a distal femoral extension osteotomy. Based on the 'Surgical Pearls for the Neuromuscularly Compromised' section, what is the MOST appropriate surgical strategy for this patient?

. Perform a full 35-degree extension osteotomy to correct the entire osseous deformity, expecting a proprioceptive reset.
. Perform a 20-degree extension osteotomy to match the clinical FFD, leaving 15 degrees of residual procurvatum.
. Perform a deliberate under-correction of the osseous deformity (e.g., 20 degrees) to utilize the remaining bony deformity as a mechanical block against hyperextension.
. Perform a 35-degree extension osteotomy combined with a posterior capsular plication to tighten the lax capsule.
. Perform a 35-degree extension osteotomy and then refer the patient for intensive hamstring strengthening rehabilitation.

Correct Answer & Explanation

. Perform a deliberate under-correction of the osseous deformity (e.g., 20 degrees) to utilize the remaining bony deformity as a mechanical block against hyperextension.

Explanation

Correct Answer: CThe case specifically highlights this exception: 'The major exception is the patient with weak, paralyzed, or atrophied hamstrings... In these patients, the dynamic checkrein is absent. ...correcting the full 30° of bone deformitywillunmask the 10° of static capsular laxity, resulting in a devastating, pathologic hyperextension thrust during the stance phase of gait. In these specific, high-risk cases, the surgeon must carefully plan adeliberate under-correctionof the osseous deformity (e.g., correcting only 20° of the 30° bow) to utilize the remaining bony deformity as a mechanical block against hyperextension.' In this patient's case, correcting only 20 degrees of the 35-degree deformity would leave 15 degrees of residual procurvatum, which would then act as a mechanical block against the 15 degrees of compensatory hyperextension, preventing pathologic recurvatum.Option A is incorrectbecause the proprioceptive reset relies on a functioning neuromuscular system, which is compromised in this patient. Full correction would lead to pathologic hyperextension.Option B is incorrectbecause while 20 degrees matches the FFD, the principle is to under-correct theosseous deformityto leave a mechanical block, not just match the FFD. The example in the text shows correcting 20 of 30 degrees, leaving 10 degrees of procurvatum, which then blocks the 10 degrees of hyperextension. So, correcting 20 degrees of a 35-degree deformity is an under-correction, but the rationale is key.Option D is incorrectbecause while capsular plication might seem logical, the Paley method emphasizes bony correction and the dynamic checkrein. The text does not suggest capsular plication as the primary solution for neuromuscularly compromised patients; deliberate under-correction of the bone is the described strategy.Option E is incorrectbecause while rehabilitation is important, it cannot restore function to paralyzed or severely atrophied muscles to the extent needed to prevent pathologic hyperextension if the dynamic checkrein is truly absent. The surgical strategy must account for the permanent neuromuscular deficit.

Question 87

Topic: Physiology & Rehabilitation

A 70-year-old patient with a long-standing history of knee flexion deformity due to femoral procurvatum is being considered for surgical correction. The patient has no known neurological deficits, and clinical assessment confirms intact hamstring strength. The surgeon plans a distal femoral extension osteotomy to correct the full 30-degree osseous deformity, despite 10 degrees of compensatory joint hyperextension. According to Paley's principles for a neuromuscularly intact patient, what is the expected outcome regarding the compensatory hyperextension postoperatively?

. The 10 degrees of compensatory hyperextension will persist, leading to a floppy, hyperextended knee.
. The extension osteotomy will functionally lengthen the posterior soft tissues, exacerbating the hyperextension.
. The proprioceptive feedback loop will reset, and the hamstrings will engage to define a new, healthy terminal extension at 0 degrees.
. The patient will require a secondary posterior capsular plication to address the persistent laxity.
. The knee will remain in 10 degrees of fixed flexion due to the uncorrected soft tissue contracture.

Correct Answer & Explanation

. The proprioceptive feedback loop will reset, and the hamstrings will engage to define a new, healthy terminal extension at 0 degrees.

Explanation

Correct Answer: CThe case explicitly addresses this scenario for a neuromuscularly intact patient: 'The ideal, biomechanically sound treatment is a 30° distal femoral extension osteotomy performed precisely at the CORA. ...More importantly, dynamic knee extension is governed by proprioception. Once the bone is surgically straightened, the CNS no longer needs to aggressively force the knee into hyperextension just to achieve an upright stance. The neural feedback loop resets instantly. The hamstrings (the dynamic checkrein) engage normally to define a new, healthy terminal extension point at exactly 0°. The postoperative FFD becomes 0°, and the compensatory hyperextension vanishes.'Option A is incorrectbecause this is the fear of trainees, but the text explains why it does not happen in a neuromuscularly intact patient.Option B is incorrectbecause the extension osteotomy functionallyshortens and tightensthe posterior soft tissues, taking up the slack, not lengthening them.Option D is incorrectbecause a secondary capsular plication is not typically needed in a neuromuscularly intact patient due to the proprioceptive reset.Option E is incorrectbecause the full correction of the osseous deformity, combined with the proprioceptive reset, is expected to resolve the FFD to 0 degrees, not leave it in flexion.

Question 88

Topic: Physiology & Rehabilitation

During gait, the normal sagittal mechanical axis plumb line (from the center of the femoral head to the center of the ankle joint) passes in which relation to the knee joint, and what biomechanical advantage does this provide?

. Posterior to the knee center of rotation, preventing excessive hyperextension.
. Through the exact center of rotation, minimizing collateral ligament strain.
. Anterior to the knee center of rotation, locking the knee in extension with minimal quadriceps effort.
. Anterior to the knee center of rotation, requiring constant hamstring contraction to prevent buckling.
. Posterior to the knee center of rotation, utilizing the quadriceps to maintain stance phase stability.

Correct Answer & Explanation

. Anterior to the knee center of rotation, locking the knee in extension with minimal quadriceps effort.

Explanation

The normal sagittal mechanical axis passes anterior to the center of rotation of the knee. This creates an extension moment, allowing the knee to 'lock' efficiently during stance phase without requiring excessive active quadriceps contraction.

Question 89

Topic: Physiology & Rehabilitation

In normal sagittal plane lower extremity alignment, where does the mechanical axis line (drawn from the center of the femoral head to the center of the ankle) pass in relation to the knee joint?

. Directly through the center of the knee joint
. Posterior to the center of the knee joint
. Anterior to the center of the knee joint
. Through the posterior cortex of the tibia
. Through the patellofemoral joint

Correct Answer & Explanation

. Anterior to the center of the knee joint

Explanation

In the normal sagittal plane, the mechanical axis line passes slightly anterior to the center of the knee joint. This anterior position creates an extension moment during the stance phase, contributing to the knee's locking mechanism and efficient gait.

Question 90

Topic: Physiology & Rehabilitation

A 25-year-old male with a history of premature anterior physeal closure of the proximal tibia presents with knee pain. Radiographs demonstrate an apex posterior bony deformity. Which of the following gait abnormalities is most likely associated with this specific osseous deformity?

. Crouch gait
. Steppage gait
. Genu recurvatum thrust during stance
. Trendelenburg gait
. Stiff-knee gait

Correct Answer & Explanation

. Genu recurvatum thrust during stance

Explanation

Premature anterior physeal closure of the proximal tibia causes an osseous recurvatum deformity (apex posterior) and an increased posterior tibial slope. This leads to a genu recurvatum thrust (hyperextension) during the stance phase of gait.

Question 91

Topic: Physiology & Rehabilitation

When assessing a patient for a sagittal plane deformity of the lower extremity, understanding normal alignment is critical for surgical planning. In a normally aligned lower extremity, where does the sagittal mechanical axis (a line drawn from the center of the femoral head to the center of the ankle joint) pass relative to the knee joint, and what is its primary biomechanical effect during the stance phase of gait?

. Posterior to the knee center, creating a flexion moment
. Posterior to the knee center, creating an extension moment
. Anterior to the knee center, creating a flexion moment
. Anterior to the knee center, creating an extension moment
. Directly through the knee center, creating no moment

Correct Answer & Explanation

. Anterior to the knee center, creating an extension moment

Explanation

The normal sagittal mechanical axis passes slightly anterior to the center of rotation of the knee joint. This physiologic alignment creates a natural extension moment during the stance phase of gait, which reduces the muscular workload required by the quadriceps to maintain knee extension.

Question 92

Topic: Physiology & Rehabilitation

The case describes the pathomechanics of ligamentous failure in a malaligned knee. In a patient with a chronic genu varum deformity originating from a proximal tibial varus, which of the following best describes the long-term biomechanical consequence on the lateral compartment structures?

. Increased compressive forces leading to cartilage hypertrophy
. Constant, abnormal tensile stress leading to plastic deformation and attenuation
. Reduced adduction moment, promoting ligamentous healing
. Shift of the mechanical axis laterally, offloading the LCL
. Increased stiffness and decreased elasticity of the popliteus tendon

Correct Answer & Explanation

. Constant, abnormal tensile stress leading to plastic deformation and attenuation

Explanation

Correct Answer: BThe text explicitly details the effects of chronic medial overloading in genu varum: 'To counteract the massive adduction moment, the lateral structures—specifically the LCL, the popliteus tendon, the biceps femoris, and the posterolateral capsule—are placed under constant, abnormal tensile stress. Over months and years of thousands of daily gait cycles, these collagenous tissues undergo plastic deformation. They stretch, thin, and lose their elastic modulus, a process clinically referred to as 'soft tissue attenuation.'' This directly corresponds to option B. Options A, C, and D describe effects contrary to what is stated in the text. While increased stiffness might occur in some pathological processes, the text specifically highlights 'plastic deformation,' 'stretch,' 'thin,' and 'lose their elastic modulus,' which implies attenuation rather than increased stiffness.

Question 93

Topic: Physiology & Rehabilitation

A patient with a significant varus thrust and underlying LCL laxity during the stance phase of gait will most likely utilize which compensatory mechanism to reduce the knee adduction moment?

. Exaggerated hip flexion
. Contralateral pelvic drop
. Lateral trunk lean toward the affected side
. Medial trunk lean away from the affected side
. Circumduction gait pattern

Correct Answer & Explanation

. Lateral trunk lean toward the affected side

Explanation

A lateral trunk lean toward the affected side during the stance phase shifts the body's center of mass closer to the knee joint center. This decreases the external knee adduction moment, mitigating the varus thrust.

Question 94

Topic: Physiology & Rehabilitation

When analyzing the joint line convergence angle (JLCA) in a patient with a varus knee and a dynamic lateral thrust, what radiographic finding is most consistent with a significant soft-tissue (ligamentous) contribution to the overall varus deformity?

. A JLCA of 0 degrees on a weight-bearing AP view.
. A JLCA that is larger on a weight-bearing radiograph compared to a supine non-weight-bearing radiograph.
. A JLCA that decreases during the stance phase of gait.
. A JLCA that measures exactly 2 degrees on both stress and resting views.
. An abnormally high MPTA on the weight-bearing view.

Correct Answer & Explanation

. A JLCA that is larger on a weight-bearing radiograph compared to a supine non-weight-bearing radiograph.

Explanation

The normal JLCA is 0 to 2 degrees. In a varus knee with LCL laxity, weight-bearing forces open the lateral joint space, resulting in a larger JLCA on weight-bearing or varus stress views compared to supine views. This signifies a soft-tissue contribution to the varus.

Question 95

Topic: Physiology & Rehabilitation

A patient with a varus knee and a documented dynamic lateral thrust is scheduled for surgery. The surgeon performs a medial opening wedge high tibial osteotomy (HTO). How does this bony correction primarily address the patient's chronic lateral soft-tissue laxity?

. By functionally shortening the LCL through proximal displacement of the fibular head.
. By shifting the weight-bearing line laterally, which persistently tensions the LCL during the stance phase.
. By allowing scarring of the iliotibial band into the medial joint space.
. By directly imbricating the lateral soft tissues via a lateral hinge.
. Bony correction cannot address lateral laxity; simultaneous LCL reconstruction is always required.

Correct Answer & Explanation

. By shifting the weight-bearing line laterally, which persistently tensions the LCL during the stance phase.

Explanation

Creating a mechanical valgus alignment shifts the weight-bearing forces laterally. During the stance phase of gait, this alignment dynamically tensions the lateral structures (including the stretched LCL) and eliminates the lateral varus thrust, making LCL reconstruction unnecessary in most cases.

Question 96

Topic: Physiology & Rehabilitation

An isolated medial opening wedge high tibial osteotomy (HTO) is performed on a patient with a varus knee and unrecognized severe lateral collateral ligament (LCL) laxity. The standing mechanical axis is corrected to 0 degrees. Postoperatively, what is the most likely clinical outcome during the stance phase of gait?

. Medial joint space collapse
. Persistent lateral varus thrust
. Excessive valgus dynamic alignment
. Genu recurvatum
. Subluxation of the proximal tibiofibular joint

Correct Answer & Explanation

. Persistent lateral varus thrust

Explanation

Failing to account for LCL laxity leads to undercorrection of the true bony deformity or persistent dynamic instability. Despite static neutral alignment, the unaddressed lateral laxity will allow a dynamic varus thrust during weight-bearing.

Question 97

Topic: Physiology & Rehabilitation

A 48-year-old male presents with a long-standing, severe genu varum deformity of his left knee. Clinically, he exhibits a pronounced Trendelenburg gait on the left side, despite having normal hip abductor strength on manual muscle testing and no signs of hip pathology or nerve injury. His surgeon suspects an infra-pelvic cause. Based on the Paley principles and the provided diagram, what is the most accurate explanation for his Trendelenburg gait?

. A. The severe genu varum directly causes a primary weakness of the gluteus medius muscle.
. B. The patient compensates for the varus knee by adducting the femur, over-lengthening the gluteus medius.
. C. The compensatory femoral abduction required to place the foot flat shortens the gluteus medius, placing it on the inefficient limb of the Blix length-tension curve.
. D. The varus deformity shifts the center of gravity of the passenger unit, directly causing pelvic drop.
. E. The increased adduction moment at the knee indirectly causes a contralateral hip drop.

Correct Answer & Explanation

. C. The compensatory femoral abduction required to place the foot flat shortens the gluteus medius, placing it on the inefficient limb of the Blix length-tension curve.

Explanation

Correct Answer: CThe case content and the accompanying diagram (ch_278_fig_e43340.webp) clearly explain the infra-pelvic Trendelenburg. In severe genu varum, the mechanical axis is severely medialized. To place the foot flat on the ground and maintain a stable base of support, the patient must compensate by abducting the femur at the hip joint. This compensatory femoral abduction drastically reduces the distance between the gluteus medius's origin (iliac crest) and insertion (greater trochanter), functionally shortening and slackening the muscle. This pushes the gluteus medius onto the inefficient, descending limb of the Blix length-tension curve, making it unable to generate sufficient force to stabilize the pelvis, resulting in a Trendelenburg lurch.Option A is incorrectbecause the problem is not a primary muscle weakness or nerve injury, but rather a mechanical disadvantage due to altered muscle length, despite normal muscle bulk and innervation.Option B is incorrectbecause patients with genu varum compensate by abducting the femur, not adducting it, to avoid tripping over their own feet. Adduction would further exacerbate the problem.Option D is incorrectbecause while passenger unit shifts can affect gait, the direct cause of the infra-pelvic Trendelenburg in this scenario is the mechanical inefficiency of the gluteus medius due to its shortened length, not a direct shift of the passenger unit's center of gravity causing pelvic drop.Option E is incorrectbecause the increased adduction moment at the knee is a consequence of the varus, but the Trendelenburg is a direct result of the gluteus medius's inability to stabilize the ipsilateral pelvis due to its altered length-tension relationship, not an indirect contralateral hip drop.

Question 98

Topic: Physiology & Rehabilitation

A 55-year-old female presents with a long-standing history of medial compartment osteoarthritis and a varus knee deformity. During your clinical gait analysis, you observe her exhibiting a noticeable lateral trunk shift over the stance limb. Based on the provided case, what is the primary biomechanical purpose of this compensatory gait pattern, and what is a critical implication for the reconstructing surgeon?

. To increase the adductor moment arm at the knee, thereby strengthening the medial collateral ligament.
. To shift the body's center of gravity medially, increasing the load on the lateral compartment for pain relief.
. To move the ground reaction force vector closer to the center of the malaligned knee, reducing compressive forces on the medial compartment, but potentially masking the true deformity severity.
. To improve the efficiency of the swing phase by reducing the metabolic energy cost of walking.
. To compensate for a fixed flexion deformity of the knee, allowing for a more plantigrade foot strike.

Correct Answer & Explanation

. To move the ground reaction force vector closer to the center of the malaligned knee, reducing compressive forces on the medial compartment, but potentially masking the true deformity severity.

Explanation

Correct Answer: CThe case describes the Duchenne or compensated Trendelenburg gait, stating: 'By lurching the torso laterally over the stance limb during the gait cycle, the patient physically shifts their overall center of gravity. This action moves the ground reaction force vector closer to the center of the malaligned knee joint. This lateral shift effectively shortens the lever arm of the adductor moment at the knee, significantly reducing the compressive forces on the overloaded, painful medial compartment.' It also critically notes, 'this dynamic compensation can easily mask the true severity of the underlying mechanical malalignment during a casual clinical gait observation.'Option A is incorrectbecause the purpose is toreducethe adductor moment arm, thereby decreasing compressive forces, not increasing it.Option B is incorrect; the shift is lateral, moving the GRF closer to the center of the knee, which reduces the medial compartment load, but does not primarily increase lateral compartment load for pain relief in this context.Option D is incorrect; the case states this gait is 'biomechanically inefficient and highly fatiguing,' not energy-efficient.Option E is incorrect; a Duchenne gait compensates for coronal plane varus deformity and medial compartment pain, not a fixed flexion deformity, which has different compensatory mechanisms (e.g., flat-foot strike, shortened step length).

Question 99

Topic: Physiology & Rehabilitation

A 38-year-old patient presents with a history of knee trauma resulting in a chronic, rigid right knee flexion deformity, measured at 24° on examination. During gait analysis, the patient demonstrates a distinct gait pattern. Based on the provided case, which of the following is the most accurate description of the biomechanical consequences of this specific deformity on the patient's gait?

. The patient will primarily utilize a heel strike, enhancing the heel rocker mechanism and shock absorption.
. The limb is functionally lengthened, leading to a compensatory circumduction gait to clear the foot.
. The inability to achieve full extension during terminal swing results in a functionally shortened limb, requiring a flat-foot or forefoot strike and increased metabolic energy cost.
. The primary compensation will be a Duchenne trunk shift to reduce medial compartment loading.
. The knee flexion deformity will primarily affect the swing phase, with minimal impact on stance phase stability.

Correct Answer & Explanation

. The inability to achieve full extension during terminal swing results in a functionally shortened limb, requiring a flat-foot or forefoot strike and increased metabolic energy cost.

Explanation

Correct Answer: CThe case states: 'A true Fixed Flexion Deformity (FFD)... has devastating, immediate effects on the gait cycle.' It further explains, 'As shown in the diagram above featuring a 24° right knee flexion deformity, a patient with an FFD has a functionally shortened limb. To make ground contact, they cannot utilize a heel strike; they must land with a 'flat-foot strike' or even a forefoot strike. This completely eliminates the heel rocker, drastically reduces the limb's shock-absorbing capacity, and skyrockets the metabolic energy cost of walking. Furthermore, the inability to fully extend the knee during terminal swing severely shortens the achievable step length, resulting in a highly asymmetric, limping gait.'Option A is incorrectbecause FFD eliminates the heel rocker and forces a flat-foot or forefoot strike.Option B is incorrectbecause an FFD results in a functionallyshortenedlimb, not lengthened. Circumduction is typically seen with a functionally lengthened limb (e.g., rigid ankle equinus without knee compensation, or LLD).Option D is incorrect; a Duchenne gait compensates for coronal plane varus and medial compartment pain, not a fixed flexion deformity.Option E is incorrect; FFD significantly impacts both swing (shortened step length due to inability to extend) and stance (loss of heel rocker, poor shock absorption, increased energy cost).

Question 100

Topic: Physiology & Rehabilitation

What is the normal average mechanical Lateral Distal Tibial Angle (mLDTA) used as a radiographic reference goal during the coronal plane correction of a distal tibial deformity?

. 75 degrees
. 80 degrees
. 84 degrees
. 89 degrees
. 95 degrees

Correct Answer & Explanation

. 89 degrees

Explanation

The normal mLDTA is approximately 89 degrees (range 86-92 degrees). Achieving this angle ensures the ankle joint line is parallel to the ground during the stance phase of gait.

Test Yourself

Switch to an interactive, timed exam simulation to truly master this topic.

On this Page