This practice set contains high-yield board review questions covering key concepts in 8. Foot and Ankle. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.
Question 1381
Topic: 8. Foot and Ankle
A 16-year-old male is undergoing a 5 cm tibial lengthening using a circular external fixator. No internal fixation of the distal tibiofibular joint was performed prior to the initiation of distraction. During the lengthening process, what ankle deformity is most likely to develop as a result of this technical omission?
Correct Answer & Explanation
. Ankle valgus
Explanation
During tibial lengthening, the intact soft tissues will pull the distal fibula proximally if it is not secured to the tibia. Proximal migration of the lateral malleolus leads to a loss of lateral talar support and subsequent ankle valgus deformity.
Question 1382
Topic: 8. Foot and Ankle
A 3-year-old boy presents with progressive bilateral genu varum. Standing radiographs demonstrate a sharply localized varus deformity at the proximal medial tibial metaphysis with a metaphyseal-diaphyseal angle (Drennan angle) of 18 degrees. He is diagnosed with Blount disease (Langenskiöld stage II). What is the initial recommended treatment?
Correct Answer & Explanation
. Knee-ankle-foot orthosis (KAFO) bracing
Explanation
In infantile Blount disease (stages I-II) in a child under age 3-4, KAFO bracing is the initial treatment of choice. Surgery is indicated if bracing fails, the child is older than 4, or the disease is advanced (stage III+).
Question 1383
Topic: 8. Foot and Ankle
During a 6 cm tibial lengthening using an Ilizarov frame, a patient develops a progressive equinus deformity of the foot despite daily physical therapy. The most likely cause of this complication is:
Correct Answer & Explanation
. Relative shortening and tightness of the gastrocnemius-soleus complex
Explanation
As the tibia is lengthened, the surrounding soft tissues, particularly the Achilles tendon and gastrosoleus complex, become relatively tight and resist stretch. This commonly leads to an equinus contracture if not aggressively managed with physical therapy, splinting, or surgical lengthening.
Question 1384
Topic: 8. Foot and Ankle
A 68-year-old male presents with chronic right knee pain and a progressive bowing deformity. A full-length weight-bearing radiograph is obtained, as shown. Based on the principles of deformity correction, what is the most accurate description of the mechanical axis deviation (MAD) in this patient?
Correct Answer & Explanation
. The mechanical axis passes medial to the knee center, indicating a varus deformity and medial compartment overload.
Explanation
Correct Answer: CThe image clearly depicts a varus deformity, where the limb bows outwards, and the mechanical axis (the line from the femoral head to the ankle) passes medial to the center of the knee joint. The text states, "In a varus malalignment, the mechanical axis passesmedialto the center of the knee. This severely overloads the medial compartment of the joint, compressing the articular cartilage and accelerating medial compartment osteoarthritis."Option A describes a valgus deformity. Option B describes normal alignment. Option D incorrectly associates a medial mechanical axis with a valgus deformity and lateral overload. Option E is incorrect as the mechanical axis and its deviation are clearly visible and interpretable in the provided full-length radiograph.
Question 1385
Topic: 8. Foot and Ankle
A 58-year-old male presents with chronic right knee pain, worse with activity. Clinical examination reveals a varus thrust during gait. A full-length, weight-bearing radiograph is obtained, as shown below, to assess the overall limb alignment. Based on the Paley principles, what is the MOST critical initial measurement to quantify the overall limb alignment in the frontal plane and guide further investigation?
Correct Answer & Explanation
. Mechanical Axis Deviation (MAD)
Explanation
Correct Answer: CThe Mechanical Axis Deviation (MAD) is universally recognized as the single most important measurement for quantifying overall limb alignment in the frontal plane. It serves as the initial, definitive indicator that a structural problem exists and dictates the urgency and scale of the required intervention. It is defined as the distance the mechanical axis (line from femoral head center to ankle mortise center) deviates from the center of the knee joint. An abnormal MAD prompts further investigation using joint orientation angles to pinpoint the deformity's source.Option A (mLDFA)andOption B (MPTA)are joint orientation angles used to pinpoint the specific bone segment responsible for the deformityafteran abnormal MAD has been identified. They are not the initial overall limb alignment measurement.Option D (JLCA)measures the angle between the distal femoral and proximal tibial joint lines and primarily suggests intra-articular pathology like cartilage loss or ligamentous laxity, not the overall limb alignment.Option E (AAD), or Anatomic Axis Deviation, is not a standard, universally recognized primary measurement for overall limb alignment in the frontal plane in the same way MAD is. While anatomic axes are used in planning, the mechanical axis is paramount for overall load-bearing assessment.
Question 1386
Topic: 8. Foot and Ankle
A 32-year-old male presents with chronic right knee pain and a progressive varus deformity. A full-length weight-bearing AP radiograph of the lower extremities is obtained for surgical planning. Which of the following is the MOST critical technical requirement for this radiograph to ensure accurate deformity analysis?
Correct Answer & Explanation
. D. The patient must be standing with patellae pointing straight ahead.
Explanation
Correct Answer: DThe most critical technical requirement for a full-length, weight-bearing AP radiograph for deformity analysis is that the patient must be standing with the patellae pointing straight ahead. This ensures that the true mechanical forces acting on the limb are captured (weight-bearing), and eliminates rotational malalignment (patellae forward) which can lead to parallax error and inaccurate frontal plane measurements. Without this, any attempt at correction is merely guesswork, as stated in the case.Incorrect Options:A. The patient's patellae must be oriented 30 degrees externally rotated to visualize the trochlear groove.This is incorrect. Patellar orientation should be strictly forward to avoid rotational malalignment and parallax error in frontal plane analysis. External rotation would artificially alter frontal plane measurements.B. The radiograph should be taken in a supine position to minimize muscle artifact.This is incorrect. The case explicitly states that "Weight-Bearing is Non-Negotiable" because supine films mask true mechanical forces, joint space narrowing, and ligamentous laxity.C. A radiopaque calibration marker must be placed at the level of the hip joint.While a calibration marker is essential, it should be positioned at the level of the bone being measured, not specifically at the hip joint, to allow for accurate digital measurement and templating. Placing it at the hip may not be representative for measurements in the tibia or distal femur.E. The film should be centered at the knee joint with minimal inclusion of the hip and ankle.This is incorrect. The radiograph must be a full-length, hip-to-ankle film to define the mechanical axis of the entire limb, which runs from the center of the femoral head to the center of the tibial plafond. Centering only on the knee would prevent this critical measurement.
Question 1387
Topic: 8. Foot and Ankle
A 55-year-old male presents with a progressive genu varum deformity. A full-length weight-bearing radiograph shows a Mechanical Axis Deviation (MAD) of 30 mm medial to the center of the knee. To determine the source of the deformity, the surgeon measures the joint orientation angles. Which of the following findings would MOST strongly suggest a primary proximal tibial varus deformity?
Correct Answer & Explanation
. B. Medial Proximal Tibial Angle (MPTA) of 78°
Explanation
Correct Answer: BThe case states that a Medial Proximal Tibial Angle (MPTA) value <85° indicates proximal tibial varus, which is the most common source of lower limb varus deformity. An MPTA of 78° is significantly less than the normal value of 87° (±2°), strongly indicating a primary proximal tibial varus deformity as the source of the genu varum.Incorrect Options:A. Mechanical Lateral Distal Femoral Angle (mLDFA) of 80°.A normal mLDFA is 87° (±2°). A value of 80° (<85°) indicates distal femoral valgus, not varus, and would contribute to a valgus deformity, not a varus deformity.C. Joint Line Convergence Angle (JLCA) of 5°.A normal JLCA is 0-2°. A value of 5° suggests ligamentous laxity, subluxation, or severe cartilage loss in the overloaded compartment, but it does not directly identify the bone segment responsible for the angular deformity itself. It's a secondary finding.D. Mechanical Lateral Proximal Femoral Angle (mLPFA) of 95°.A normal mLPFA is 90° (±2°). A value of 95° indicates a proximal femoral valgus deformity, which would not be the primary cause of a genu varum at the knee.E. Lateral Distal Tibial Angle (LDTA) of 89°.A normal LDTA is 89° (±2°). A value of 89° is within the normal range, indicating no significant varus or valgus deformity at the ankle joint (tibial plafond).
Question 1388
Topic: Midfoot & Hindfoot
A 45-year-old female presents with a severe valgus deformity of the knee. The Joint Line Convergence Angle (JLCA) is measured at 6 degrees opening medially. What does this abnormally increased JLCA most likely indicate in the context of lower extremity deformity?
Correct Answer & Explanation
. Intra-articular deformity, cartilage wear, or medial ligamentous laxity
Explanation
The normal JLCA is 0 to 2 degrees. An increased JLCA indicates that the joint space is asymmetric, which can be caused by cartilage loss, intra-articular deformity, or collateral ligament laxity.
Question 1389
Topic: 8. Foot and Ankle
A patient has a severe primary structural valgus deformity of the distal tibia. Over time, to maintain a plantigrade foot during weight-bearing, which of the following compensatory deformities is most likely to develop?
Correct Answer & Explanation
. Subtalar varus
Explanation
To compensate for a structural valgus deformity of the distal tibia and keep the plantar surface of the foot flat on the ground (plantigrade), the subtalar joint will invert, creating a compensatory subtalar varus deformity.
Question 1390
Topic: 8. Foot and Ankle
A surgeon is performing a corrective osteotomy for a femoral deformity. The true Center of Rotation of Angulation (CORA) is located intra-articularly, making a bone cut at that exact level unsafe. The surgeon decides to perform the osteotomy 5 cm distal to the CORA. To ensure the overall mechanical axis is perfectly realigned, where must the mechanical hinge of the external fixator be placed?
Correct Answer & Explanation
. Exactly at the true CORA, despite the osteotomy being distal to it.
Explanation
Correct Answer: BThis scenario describes Paley's Osteotomy Rule 2: Angulation and Translation. The case states: 'This is the most common practical scenario encountered in the OR. It is utilized when cutting directly at the CORA is unsafe or impossible... Osteotomy Location: The bone cut is made at a safe levelaway from the CORA. Hinge Location: The hinge of the fixator is still placedexactly on the CORA. Result: Because the bone is cut away from the hinge point, the correction will result in a combination of angulation and intentional translation at the osteotomy site... However, because the hinge remained on the CORA, the overall proximal and distal mechanical axes will perfectly realign.'Therefore, to ensure perfect realignment of the mechanical axis, the hinge must be placed exactly at the true CORA, even if the osteotomy is performed at a different, safer location. Option A describes Rule 3, which leads to unintended translation. Options C and D are anatomical landmarks, not the hinge placement for a specific osteotomy. Option E is not a recognized rule for hinge placement.
Question 1391
Topic: 8. Foot and Ankle
When evaluating the ankle joint for deformity correction, the normal Lateral Distal Tibial Angle (LDTA) is measured. What is the accepted normal value for the mechanical LDTA?
Correct Answer & Explanation
. 89 degrees
Explanation
The normal Lateral Distal Tibial Angle (LDTA) is approximately 89 degrees (range 86-92 degrees). Deviation from this indicates varus (LDTA > 92) or valgus (LDTA < 86) deformity of the distal tibia.
Question 1392
Topic: 8. Foot and Ankle
A 58-year-old male presents with progressive right knee pain and a noticeable 'bow-legged' appearance. Clinical examination confirms a varus deformity. A standing full-length AP radiograph is obtained, revealing the image below. Based on Paley's principles, what is the *absolute first step* in quantifying this patient's overall limb malalignment and what is its expected finding?
Correct Answer & Explanation
. Determine the Mechanical Axis Deviation (MAD); it will pass significantly medial to the center of the knee.
Explanation
Correct Answer: CThe absolute first step in any lower extremity alignment analysis, as outlined in the case, is to quantify the overall deformity using the Mechanical Axis Deviation (MAD). The MAD is the perpendicular distance from the mechanical axis line (connecting the center of the femoral head to the center of the ankle mortise) to the center of the knee joint. For a patient presenting with a 'bow-legged' appearance, which is a varus deformity, the mechanical axis line is expected to pass significantly medial to the center of the knee. This initial measurement dictates the clinical significance of the deformity and guides the threshold for surgical intervention.Option A is incorrectbecause while measuring the mLDFA is a crucial subsequent step to determine if the femur is the source of the deformity, it is not theabsolute first stepin quantifying theoverall limb malalignment. The MAD provides the initial global assessment.Option B is incorrectfor the same reason as A. MPTA is used to assess tibial deformity, but only after the overall MAD has been established.Option D is incorrectbecause locating the CORA is a later step in the planning process, after the overall malalignment has been quantified and the specific bone(s) involved have been identified through joint orientation angles. The CORA tells youhowto fix it, notthata deformity exists or its overall magnitude.Option E is incorrectbecause the JLCA assesses intra-articular pathology like ligamentous laxity or cartilage loss, which can contribute to malalignment but is not the initial global measure of the limb's mechanical axis deviation.
Question 1393
Topic: 8. Foot and Ankle
A 62-year-old female presents with severe medial compartment osteoarthritis and a significant varus deformity of her left knee. Preoperative planning is initiated. The Malalignment Test reveals a MAD of 20mm medial to the center of the knee. Joint orientation angles are measured: mLDFA = 87°, MPTA = 100°, LDTA = 89°, JLCA = 1°. Based on these findings, which of the following best describes the next step in defining the proximal tibial mechanical axis?
Correct Answer & Explanation
. Draw a line from the center of the knee joint distally into the tibia at an angle of 87° relative to the proximal tibial joint line.
Explanation
Correct Answer: BThe case describes two scenarios for defining the proximal tibial mechanical axis. Scenario A (normal femur/knee) allows extending the femoral mechanical axis. Scenario B (deformed femur/abnormal JLCA) requires creating ade novoproximal tibial line. In this patient, the mLDFA (87°) is normal, and the JLCA (1°) is normal, which might initially suggest Scenario A. However, the MPTA is 100°, which is significantly abnormal (normal range 85°-90°). An abnormal MPTA indicates a deformity in the proximal tibia. Therefore, to define theintendednormal mechanical axis of the proximal tibial segment, you must draw a line from the center of the knee joint distally into the tibia at thenormalMPTA of 87° relative to the proximal tibial joint line. This establishes the desired orientation for correction.Option A is incorrectbecause while the mLDFA and JLCA are normal, the MPTA is abnormal (100°), indicating the proximal tibia itself is deformed. Extending the femoral mechanical axis would not correctly define thenormalproximal tibial axis when the tibia itself is maloriented.Option C is incorrectbecause drawing the line at 100° would perpetuate the existing deformity, not define the desired normal axis for correction.Option D is incorrectbecause drawing the distal mechanical axis is Step 2, not Step 1, and it's drawn from the ankle, not the knee.Option E is incorrectbecause locating the CORA is Step 3, after both proximal and distal axes have been defined.
Question 1394
Topic: 8. Foot and Ankle
A 16-year-old female presents with a progressive valgus deformity of her right lower extremity. Initial assessment reveals a significant lateral Mechanical Axis Deviation (MAD). Joint orientation angles are measured: mLDFA = 87°, MPTA = 87°, and JLCA = 1°. After establishing the proximal tibial mechanical axis, the next step involves defining the distal segment and performing the Malorientation Test (MOT). What is the primary purpose of measuring the Lateral Distal Tibial Angle (LDTA) during this step?
Correct Answer & Explanation
. To identify if there is a secondary deformity near the ankle joint.
Explanation
Correct Answer: CAs described in Step 2 of the 'Masterclass in Action,' after defining the distal mechanical axis, the Malorientation Test (MOT) is performed by measuring the LDTA. The primary purpose of the LDTA is to define the orientation of the ankle joint line relative to the tibial mechanical axis. If the LDTA is abnormal (normal range 86°-92°), it serves as a critical red flag, indicating a multiapical deformity with a secondary deformity near the ankle. This helps to ensure that all components of a complex deformity are identified.Option A is incorrectbecause the overall limb alignment is assessed by the MAD, which has already been determined to be abnormal.Option B is incorrectbecause the magnitude of the angular deformity at the CORA is determined in Step 3, by the angle formed at the intersection of the proximal and distal axis lines, not by the LDTA itself.Option D is incorrectbecause intra-articular pathology is primarily assessed by the JLCA, which is already given as normal (1°).Option E is incorrectbecause the question is focused on tibial planning, and the mLDFA is normal, ruling out a primary femoral deformity requiring a proximal femoral osteotomy.
Question 1395
Topic: 8. Foot and Ankle
A 22-year-old patient presents with a severe valgus deformity of the right lower extremity, as shown in the clinical image. Preoperative planning is initiated. Which of the following combinations of joint orientation angles would most strongly suggest that the primary deformity is located in the proximal tibia, rather than the distal femur or ankle?
Correct Answer & Explanation
. mLDFA = 87°, MPTA = 75°, LDTA = 89°
Explanation
Correct Answer: BTo identify the primary location of a deformity, we compare the measured joint orientation angles to their normal ranges. The normal values are: mLDFA (87° ± 2-3°), MPTA (87° ± 2-3°), LDTA (89° ± 3°). A valgus deformity in the proximal tibia would manifest as a decreased MPTA (i.e., the proximal tibia is angled more laterally relative to its mechanical axis).Option A:mLDFA = 78° (abnormal, valgus femur), MPTA = 87° (normal), LDTA = 89° (normal). This indicates a femoral deformity.Option B:mLDFA = 87° (normal), MPTA = 75° (abnormal, valgus tibia), LDTA = 89° (normal). This combination strongly suggests the primary deformity is in the proximal tibia.Option C:mLDFA = 87° (normal), MPTA = 87° (normal), LDTA = 78° (abnormal, valgus distal tibia/ankle). This indicates a distal tibial/ankle deformity.Option D:mLDFA = 78° (abnormal), MPTA = 75° (abnormal). This indicates a multi-level deformity involving both the femur and proximal tibia.Option E:mLDFA = 87° (normal), MPTA = 87° (normal), JLCA = 5° (abnormal). This suggests intra-articular pathology (e.g., ligamentous laxity or asymmetric cartilage loss) rather than a primary bony deformity in the proximal tibia.Therefore, mLDFA = 87°, MPTA = 75°, LDTA = 89° is the combination that most strongly points to a primary proximal tibial deformity.
Question 1396
Topic: 8. Foot and Ankle
A 70-year-old patient presents with severe medial compartment osteoarthritis of the knee, attributed to a long-standing varus deformity. Which of the following is the most direct biomechanical consequence of this uncorrected malalignment?
Correct Answer & Explanation
. Abnormal, asymmetrical load distribution across the knee and ankle cartilage.
Explanation
Correct Answer: CThe case clearly states, 'Any pathologic deviation of this line—whether medial (varus) or lateral (valgus)—results in abnormal, asymmetrical load distribution across the knee and ankle cartilage. This malalignment is a primary driver of premature joint degeneration, functional impairment, meniscal tearing, and chronic pain.' In a varus deformity, the mechanical axis passes medial to the knee center, leading to increased compressive forces and asymmetrical loading on the medial compartment cartilage and meniscus, accelerating degeneration.
Question 1397
Topic: 8. Foot and Ankle
A surgeon is evaluating a full-length standing radiograph for a patient with suspected distal tibial deformity. To assess the orientation of the ankle joint relative to the tibial mechanical axis, which angle is measured, and what is its normal average value?
Correct Answer & Explanation
. Lateral Distal Tibial Angle (LDTA); 89°
Explanation
Correct Answer: DThe table in the case explicitly defines the Lateral Distal Tibial Angle (LDTA) as the angle that 'Evaluates the orientation of the ankle joint relative to the tibial mechanical axis.' It lists the normal average value for LDTA as 89°, with a range of 86° to 92°. The other options refer to different angles or incorrect normal values for the specified angle.
Question 1398
Topic: 8. Foot and Ankle
A 50-year-old female presents with bilateral knee pain. A full-length standing AP radiograph reveals a mechanical axis deviation (MAD) of 20 mm medial to the center of the right knee. The mechanical lateral distal femoral angle (mLDFA) is 87° and the medial proximal tibial angle (MPTA) is 78°. Where is the primary source of the malalignment?
Correct Answer & Explanation
. Tibia
Explanation
The normal MPTA is 87° (range 85°-90°), and the normal mLDFA is 87° (range 85°-90°). An MPTA of 78° indicates a proximal tibial varus deformity, which is the primary source of the medial MAD.
Question 1399
Topic: 8. Foot and Ankle
A patient is evaluated for an ankle deformity following a distal tibia malunion. The Lateral Distal Tibial Angle (LDTA) is measured at 100° on the AP radiograph. What clinical deformity does this measurement indicate?
Correct Answer & Explanation
. Ankle valgus
Explanation
The normal LDTA is approximately 89° (range 86°-92°). An LDTA of 100° indicates that the distal tibial articular surface is tilted laterally, resulting in an ankle valgus deformity.
Question 1400
Topic: 8. Foot and Ankle
Which of the following interventions is most critical to consider when performing a massive acute correction of a severe proximal tibial valgus and flexion deformity?
Correct Answer & Explanation
. Prophylactic common peroneal nerve decompression
Explanation
Correcting a severe valgus or flexion deformity of the knee stretches the lateral and posterior structures. The common peroneal nerve is particularly tethered at the fibular neck and is at high risk of palsy, often requiring prophylactic decompression.
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