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1. General Principles & Basic Science MCQs

Practice Set 219 of 789

This practice set contains high-yield board review questions covering key concepts in 1. General Principles & Basic Science. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 4361

Topic: 1. General Principles & Basic Science

A 6-year-old boy presents with a painless clicking and "snapping" sensation in his lateral knee during terminal extension. MRI confirms a Wrisberg variant of a lateral discoid meniscus. What is the defining anatomic feature of this meniscal variant?

. Lack of the posterior meniscofemoral ligament
. Lack of the posterior meniscotibial (coronary) ligament
. Anomalous insertion of the anterior horn into the ACL
. Thickened anterior meniscofemoral ligament
. Medial meniscal hypoplasia

Correct Answer & Explanation

. Lack of the posterior meniscotibial (coronary) ligament

Explanation

The Wrisberg variant of a discoid meniscus lacks the normal posterior meniscotibial (coronary) ligament attachments, making it highly mobile. It attaches posteriorly only via the meniscofemoral ligament of Wrisberg, leading to the classic "snapping" knee upon extension.

Question 4362

Topic: 1. General Principles & Basic Science

In the structural organization of articular cartilage, which zone is characterized by the lowest concentration of water, the highest concentration of proteoglycans, and collagen fibers oriented perpendicular to the joint surface?

. Superficial zone
. Transitional (middle) zone
. Deep zone
. Calcified zone
. Tidemark

Correct Answer & Explanation

. Deep zone

Explanation

The deep zone of articular cartilage contains the highest concentration of proteoglycans and the lowest water content. Its collagen fibers (primarily Type II) are arranged perpendicular to the articular surface to provide maximum resistance to compressive forces. The superficial zone has the highest water content and collagen aligned parallel to the surface to resist shear forces.

Question 4363

Topic: Biology, Genetics & Bone Healing

The biomechanical properties of articular cartilage are dependent on its extracellular matrix. Which of the following components is primarily responsible for generating the tissue's compressive stiffness through osmotic swelling pressure?

. Type I collagen
. Type II collagen
. Aggrecan
. Elastin
. Fibronectin

Correct Answer & Explanation

. Aggrecan

Explanation

Aggrecan is the most abundant proteoglycan in articular cartilage. Its highly negatively charged glycosaminoglycan (GAG) side chains attract water, creating a strong osmotic swelling pressure. This swelling is resisted by the tensile strength of the Type II collagen network, providing articular cartilage with its characteristic compressive stiffness.

Question 4364

Topic: Biology, Genetics & Bone Healing

When a full-thickness articular cartilage defect extends through the tidemark into the subchondral bone, marrow-derived mesenchymal stem cells fill the defect. The resulting repair tissue is biomechanically inferior to native hyaline cartilage. Which type of collagen predominates in this repair tissue?

. Type I collagen
. Type II collagen
. Type IX collagen
. Type X collagen
. Type XI collagen

Correct Answer & Explanation

. Type I collagen

Explanation

Defects that penetrate the subchondral bone heal via the formation of fibrocartilage. Unlike native articular hyaline cartilage, which is predominantly composed of Type II collagen, fibrocartilage is primarily composed of Type I collagen. Type I collagen lacks the complex structural organization needed to resist the compressive and shear forces of the joint, leading to earlier degradation.

Question 4365

Topic: 1. General Principles & Basic Science

In the pathogenesis of osteoarthritis, matrix degradation outpaces synthesis. Which matrix metalloproteinase (MMP) is considered the primary and most potent enzyme responsible for the cleavage of Type II collagen in articular cartilage?

. MMP-1
. MMP-3
. MMP-9
. MMP-13
. MMP-14

Correct Answer & Explanation

. MMP-13

Explanation

MMP-13 (collagenase-3) is the primary enzyme responsible for the degradation of Type II collagen in articular cartilage during osteoarthritis. While MMP-1 also cleaves fibrillar collagen, MMP-13 is significantly more efficient at cleaving Type II collagen and is heavily upregulated in osteoarthritic chondrocytes.

Question 4366

Topic: 1. General Principles & Basic Science

Articular cartilage is an avascular tissue, forcing chondrocytes to survive in a deeply hypoxic environment. Which primary transcription factor is upregulated in chondrocytes to mediate their survival, regulate energy metabolism, and maintain extracellular matrix synthesis under these low-oxygen conditions?

. Runx2
. Sox9
. HIF-1 alpha
. NF-kappa B
. SMAD3

Correct Answer & Explanation

. HIF-1 alpha

Explanation

Hypoxia-inducible factor 1-alpha (HIF-1 alpha) is the master transcriptional regulator of the cellular response to hypoxia. In the avascular articular cartilage, HIF-1 alpha is essential for chondrocyte survival, promoting glycolysis for ATP generation and supporting the synthesis of Sox9, Type II collagen, and aggrecan.

Question 4367

Topic: 1. General Principles & Basic Science

Which zone of articular cartilage has the highest concentration of water and the lowest concentration of proteoglycans, with collagen fibrils oriented parallel to the joint surface?

. Superficial (tangential) zone
. Transitional (middle) zone
. Deep (radial) zone
. Calcified zone
. Subchondral bone layer

Correct Answer & Explanation

. Superficial (tangential) zone

Explanation

The superficial (tangential) zone of articular cartilage contains the highest water content (up to 80%) and the lowest concentration of proteoglycans. The collagen fibrils (primarily Type II) are oriented parallel to the articular surface to resist shear forces and provide tensile strength.

Question 4368

Topic: 1. General Principles & Basic Science

A 45-year-old woman with Stage IIb adult-acquired flatfoot deformity is undergoing reconstruction. During the lateral column lengthening (Evans calcaneal osteotomy), which of the following structures is at greatest risk of iatrogenic injury if the saw blade exits too plantar and distal?

. Sural nerve
. Peroneus brevis tendon
. Peroneus longus tendon
. Lateral plantar nerve
. Calcaneofibular ligament

Correct Answer & Explanation

. Peroneus longus tendon

Explanation

During an Evans calcaneal osteotomy (which is performed approximately 1 to 1.5 cm proximal to the calcaneocuboid joint), the peroneus longus tendon is at greatest risk of injury. It courses obliquely along the plantar aspect of the cuboid groove, placing it in jeopardy if the osteotomy penetrates too deeply in the plantar-distal direction.

Question 4369

Topic: Biology, Genetics & Bone Healing
In the structural composition of native adult hyaline articular cartilage, which minor collagen primarily functions to cross-link fibrillar elements and regulate the diameter of the collagen fibrils?
. Type I collagen
. Type II collagen
. Type IX collagen
. Type X collagen
. Type I and III collagen

Correct Answer & Explanation

. Type IX collagen

Explanation

While Type II collagen constitutes 90-95% of the collagen in articular cartilage and provides the primary structural framework, Type IX (along with Type XI) is a minor collagen that plays a crucial role in covalently cross-linking the Type II fibrils, thereby regulating their diameter and stabilizing the matrix. Type X collagen is exclusively found in the calcified zone.

Question 4370

Topic: 1. General Principles & Basic Science

Which portion of the spring ligament complex (plantar calcaneonavicular ligament) is anatomically the strongest, attaches to the navicular tuberosity, and acts as the primary static restraint to plantar-medial subluxation of the talar head?

. Superomedial calcaneonavicular ligament
. Inferior plantar calcaneonavicular ligament
. Medioplantar oblique ligament
. Cervical ligament
. Interosseous talocalcaneal ligament

Correct Answer & Explanation

. Superomedial calcaneonavicular ligament

Explanation

The spring ligament is essential for supporting the medial longitudinal arch. The superomedial calcaneonavicular ligament is the broadest and strongest portion of this complex. It provides the primary hammock-like support beneath the talar head, preventing its plantar and medial subluxation in conditions like adult-acquired flatfoot deformity.

Question 4371

Topic: 1. General Principles & Basic Science

Which large aggregating proteoglycan is the most abundant in articular cartilage, playing a pivotal role in retaining water within the extracellular matrix to resist compressive loads?

. Decorin
. Biglycan
. Aggrecan
. Fibromodulin
. Lumican

Correct Answer & Explanation

. Aggrecan

Explanation

Aggrecan is the predominant large proteoglycan in articular cartilage. It consists of a protein core with numerous glycosaminoglycan (GAG) side chains (chondroitin sulfate and keratan sulfate). These highly negatively charged GAGs attract sodium and water, creating the massive osmotic swelling pressure that imparts cartilage with its ability to withstand significant compressive loads.

Question 4372

Topic: Surgical Anatomy & Approaches

When performing the extended volar (Henry) approach to the distal radius and forearm, the surgeon exploits the internervous plane in the proximal forearm between the flexor carpi radialis (FCR) and the brachioradialis. This represents a safe interval between the territories of which two nerves?

. Median and Ulnar nerves
. Radial and Musculocutaneous nerves
. Median and Radial nerves
. Anterior Interosseous and Radial nerves
. Radial and Ulnar nerves

Correct Answer & Explanation

. Median and Radial nerves

Explanation

The volar Henry approach to the radius utilizes the internervous plane between the brachioradialis (innervated by the radial nerve) and the flexor carpi radialis (innervated by the median nerve). Retracting the brachioradialis laterally and the FCR medially provides access to the pronator teres and flexor pollicis longus, beneath which the radius lies.

Question 4373

Topic: 1. General Principles & Basic Science

In the pathogenesis of osteoarthritis, which matrix metalloproteinase (MMP) is considered the most critical enzyme responsible for the direct cleavage and irreversible degradation of the Type II collagen fibrillar network?

. MMP-1
. MMP-2
. MMP-3
. MMP-9
. MMP-13

Correct Answer & Explanation

. MMP-13

Explanation

MMP-13 (collagenase-3) is heavily implicated in osteoarthritis. It is highly overexpressed in OA cartilage and has a strong preference for cleaving Type II collagen, leading to the irreversible breakdown of the primary structural framework of articular cartilage. MMP-3 (stromelysin-1) primarily degrades proteoglycans, while MMP-1 plays a lesser role in Type II collagen degradation.

Question 4374

Topic: 1. General Principles & Basic Science

In the microscopic anatomy of mature articular cartilage, the 'tidemark' serves as the histological boundary delineating which of the following structures?

. The superficial tangential zone from the middle transitional zone
. The middle transitional zone from the deep radial zone
. The deep radial uncalcified zone from the calcified zone
. The calcified zone from the subchondral bone plate
. The articular cartilage from the synovial reflection

Correct Answer & Explanation

. The deep radial uncalcified zone from the calcified zone

Explanation

The tidemark is a metabolically active histological boundary that separates the deep (radial), uncalcified hyaline cartilage from the calcified cartilage zone. It is recognizable on H&E staining as a distinct basophilic line. The zone below the tidemark is tethered directly to the subchondral bone via the cement line.

Question 4375

Topic: 1. General Principles & Basic Science

In normal articular cartilage, which zone is characterized by the highest concentration of proteoglycans, the lowest concentration of water, and collagen fibrils aligned perpendicular to the articular surface?

. Superficial zone
. Middle (transitional) zone
. Deep (radial) zone
. Calcified cartilage zone
. Subchondral bone plate

Correct Answer & Explanation

. Deep (radial) zone

Explanation

The deep (radial) zone of articular cartilage contains the highest concentration of proteoglycans, the lowest water content, and the largest diameter collagen fibrils. These fibrils are oriented perpendicular to the joint surface to effectively resist and distribute compressive loads. In contrast, the superficial zone has the highest water content and lowest proteoglycan concentration.

Question 4376

Topic: 1. General Principles & Basic Science
In the pathogenesis of osteoarthritis, which matrix metalloproteinase (MMP) is recognized as the primary enzyme responsible for the cleavage and degradation of Type II collagen in articular cartilage?
. MMP-1
. MMP-3
. MMP-9
. MMP-13
. MMP-14

Correct Answer & Explanation

. MMP-13

Explanation

MMP-13 (collagenase-3) is heavily upregulated in osteoarthritic cartilage and is the principal enzyme responsible for the irreversible degradation of Type II collagen. MMP-3 (stromelysin) primarily degrades proteoglycans (aggrecan), while MMP-1 is more active against Type I and III collagens.

Question 4377

Topic: Biology, Genetics & Bone Healing

Lubricin (PRG4) is a critical glycoprotein for boundary lubrication in synovial joints. Which cells are primarily responsible for synthesizing and secreting lubricin in healthy articular cartilage?

. Superficial zone chondrocytes
. Middle zone chondrocytes
. Deep zone chondrocytes
. Subchondral osteoblasts
. Fibroblasts in the joint capsule

Correct Answer & Explanation

. Superficial zone chondrocytes

Explanation

Lubricin (proteoglycan 4 or PRG4) is synthesized primarily by superficial zone chondrocytes and synoviocytes. It localizes to the articular surface where it provides crucial boundary lubrication, significantly reducing friction and wear during joint movement.

Question 4378

Topic: 1. General Principles & Basic Science

Which of the following zones of normal articular cartilage contains the lowest concentration of water, the highest concentration of proteoglycans, and collagen fibers oriented strictly perpendicular to the articular surface?

. Superficial zone
. Transitional (middle) zone
. Deep zone
. Calcified zone
. Subchondral bone

Correct Answer & Explanation

. Deep zone

Explanation

The deep (basal) zone of articular cartilage is characterized by the lowest water content, the highest proteoglycan content, and large-diameter Type II collagen fibers oriented perpendicular to the articular surface. This architecture provides maximum resistance to compressive forces. The superficial zone has the highest water content and collagen fibers parallel to the joint surface to resist shear forces.

Question 4379

Topic: 1. General Principles & Basic Science

Boundary lubrication of normal articular cartilage is essential for minimizing friction during low-speed, high-load conditions. Which specific molecule is primarily responsible for boundary lubrication at the cartilage surface?

. Hyaluronic acid
. Aggrecan
. Type II collagen
. Lubricin (PRG4)
. Chondroitin sulfate

Correct Answer & Explanation

. Lubricin (PRG4)

Explanation

Lubricin, also known as proteoglycan 4 (PRG4), is a glycoprotein secreted by superficial zone chondrocytes and synovial fibroblasts. It is the primary molecule responsible for boundary lubrication of articular cartilage, physically binding to the articular surface to reduce friction and prevent wear during low-speed, high-load interactions. Hyaluronic acid contributes to fluid-film lubrication but is not the primary boundary lubricant.

Question 4380

Topic: 1. General Principles & Basic Science

A 45-year-old male presents with isolated weakness when attempting to pinch his thumb and index finger together, specifically unable to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger (positive "OK" sign). He has normal sensation. Compression of the involved nerve is most likely caused by which anomalous structure?

. Superficial head of the pronator teres
. Arcade of Frohse
. Lacertus fibrosus
. Accessory head of the flexor pollicis longus (Gantzer's muscle)
. Ligament of Struthers

Correct Answer & Explanation

. Accessory head of the flexor pollicis longus (Gantzer's muscle)

Explanation

The patient has Anterior Interosseous Nerve (AIN) syndrome, indicated by weakness of the flexor pollicis longus (FPL), flexor digitorum profundus (FDP) to the index/middle fingers, and pronator quadratus, without sensory deficits. Gantzer's muscle, which is an accessory head of the FPL, is a well-known anatomical anomaly that can compress the AIN. The Arcade of Frohse compresses the PIN.

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