Arthrology and Infections — MCQs

Arthrology and Infections Indian Medical PG Practice Questions and MCQs

Question 21: A child presents with a swollen, painful knee and high fever, with no history of trauma. Acute osteomyelitis is suspected. Which part of the bone is earliest involved in hematogenous osteomyelitis?

A. Metaphysis (Correct Answer)
B. Diaphysis
C. Epiphysis
D. Area around the nutrient artery

Explanation: ### Explanation **Correct Option: A. Metaphysis** In children, hematogenous osteomyelitis most commonly involves the **metaphysis** of long bones. This is due to the unique vascular anatomy of the growing skeleton: 1. **Hairpin Loops:** The nutrient artery ends in sharp, 180-degree loops (hairpin loops) just below the epiphyseal growth plate. This causes sudden slowing and turbulence of blood flow. 2. **Sluggish Circulation:** The slow blood flow in these wide venous sinusoids allows bacteria to settle and proliferate. 3. **Deficient Phagocytosis:** The capillary loops in this region lack a robust population of phagocytic cells (macrophages), making it an ideal site for infection. --- ### Why other options are incorrect: * **B. Diaphysis:** While infection can spread to the diaphysis via the medullary canal, it is rarely the primary site of origin, except in specific conditions like **Ewing’s Sarcoma** (a common differential) or **Sickle Cell Anemia** (where *Salmonella* can cause diaphyseal infarcts). * **C. Epiphysis:** The growth plate (physis) acts as a physical barrier to the spread of infection in children. The epiphysis is usually spared unless the infection is extremely aggressive or the child is an infant (where trans-physeal vessels exist). * **D. Area around the nutrient artery:** While the nutrient artery carries the bacteria, the infection does not seed in the high-pressure main trunk; it seeds where the flow slows down (the terminal branches in the metaphysis). --- ### High-Yield Clinical Pearls for NEET-PG: * **Most common organism:** *Staphylococcus aureus* (overall). * **Most common organism in Sickle Cell patients:** *Salmonella*. * **Earliest Sign on X-ray:** Soft tissue swelling (visible at 24–48 hours). Bony changes (periosteal reaction/rarefaction) take **7–14 days** to appear. * **Investigation of Choice:** **MRI** is the most sensitive and specific early imaging modality. * **Joint Involvement:** If the metaphysis is **intracapsular** (e.g., hip, shoulder, ankle, elbow), osteomyelitis can lead to **Septic Arthritis**.

Question 22: Charcot's joint is another name for a joint affected by which condition?

A. Neuropathy (Correct Answer)
B. Osteoarthritis
C. Rheumatoid arthritis
D. Ankylosing spondylitis

Explanation: **Explanation:** **Charcot’s Joint**, also known as **Neuropathic Arthropathy**, is a progressive degenerative condition characterized by joint destruction, pathological fractures, and joint instability. It occurs due to a loss of protective sensation (pain and proprioception) in the joint. 1. **Why Neuropathy is Correct:** The underlying mechanism involves repetitive microtrauma to a joint that cannot sense pain. This leads to inflammatory bone resorption and structural collapse. Common causes include **Diabetes Mellitus** (most common, typically affecting the foot/ankle), **Syringomyelia** (typically affecting the shoulder), and **Tabes Dorsalis** (historically affecting the knee). 2. **Why Incorrect Options are Wrong:** * **Osteoarthritis:** This is a primary "wear and tear" degenerative disease of the articular cartilage, not primarily driven by sensory loss. * **Rheumatoid Arthritis:** This is an autoimmune, inflammatory systemic disease primarily affecting the synovium. * **Ankylosing Spondylitis:** This is a seronegative spondyloarthropathy characterized by enthesitis and joint fusion (ankylosis), rather than the "bag of bones" destruction seen in Charcot’s. **High-Yield Clinical Pearls for NEET-PG:** * **The 6 D’s of Charcot’s Joint:** Distension, Density (increased), Debris, Dislocation, Disorganization, and Destruction. * **Clinical Paradox:** The joint often appears severely deformed and swollen (the "bag of bones" appearance) but is remarkably **painless** or much less painful than the X-ray suggests. * **French Theory:** Suggests a neurovascular component where autonomic dysfunction leads to hyperemic bone resorption. * **Differential Diagnosis:** It is often confused with Osteomyelitis; however, Charcot’s typically presents with a rapid onset of deformity without significant systemic signs of infection.

Question 23: Monoarticular joint involvement is seen in which of the following?

A. Primary osteoarthritis
B. Rheumatoid arthritis
C. Tubercular arthritis (Correct Answer)
D. Seronegative spondyloarthritis

Explanation: **Explanation:** The pattern of joint involvement is a critical diagnostic clue in orthopaedics. **Tubercular arthritis** is the correct answer because it typically presents as a **chronic, progressive monoarthritis**. In India, the hip and knee are the most common peripheral joints affected. The pathology involves a slow, granulomatous destruction of a single joint, often characterized by the "Phemister triad" (juxta-articular osteopenia, peripheral erosions, and gradual joint space narrowing). **Analysis of Incorrect Options:** * **Primary Osteoarthritis (OA):** This is a degenerative condition that is typically **polyarticular and bilateral**, commonly affecting weight-bearing joints (knees, hips) and the small joints of the hands (Heberden’s and Bouchard’s nodes). * **Rheumatoid Arthritis (RA):** This is a classic **symmetrical inflammatory polyarthritis**. It predominantly involves small joints of the hands and feet (MCP, PIP joints) and spares the DIP joints. * **Seronegative Spondyloarthritis (SpA):** This group (e.g., Ankylosing Spondylitis, Psoriatic Arthritis) typically presents as an **asymmetrical oligoarthritis** (affecting 2–4 joints) or involves the axial skeleton (sacroiliitis). **High-Yield Clinical Pearls for NEET-PG:** * **Monoarthritis Differential:** Always rule out **Septic arthritis** (acute) and **Tubercular arthritis** (chronic) in cases of single joint involvement. * **TB Spine (Pott’s Disease):** The most common site of skeletal TB is the spine (thoracolumbar junction). * **Night Starts:** A characteristic feature of joint TB where pain occurs at night when the protective muscle splinting relaxes, allowing the inflamed articular surfaces to rub together. * **Cold Abscess:** A hallmark of TB, where a collection of pus forms without the typical signs of inflammation (heat, redness).

Question 24: A patient has a history of similar symptoms at the same site two years ago, developing pain and swelling. X-ray shows the following features. What is the diagnosis?

A. Osteogenic sarcoma
B. Ewing's sarcoma
C. Chronic osteomyelitis (Correct Answer)
D. Multiple myeloma

Explanation: ***Chronic osteomyelitis*** - History of **recurrent pain and swelling** at the same site over 2 years is pathognomonic for chronic osteomyelitis with periodic **exacerbations**. - X-ray features include **sequestrum** (dead bone), **involucrum** (new bone formation), **cortical sclerosis**, and **periosteal reaction**. *Osteogenic sarcoma* - Typically presents as a **primary malignancy** in adolescents/young adults without history of recurrent episodes at the same site. - X-ray shows characteristic **sunburst appearance** and **Codman's triangle**, not the mixed sclerotic-lytic pattern of chronic osteomyelitis. *Ewing's sarcoma* - Usually affects children and adolescents as an **aggressive primary bone tumor** without chronic recurrent history. - X-ray demonstrates **onion-skin periosteal reaction** and **permeative bone destruction**, distinct from chronic osteomyelitis findings. *Multiple myeloma* - Presents in **older adults** (>60 years) with systemic symptoms like bone pain, anemia, and hypercalcemia. - X-ray shows characteristic **punched-out lytic lesions** without sclerosis or periosteal reaction, unlike chronic osteomyelitis.

Question 25: Tuberculous arthritis of a joint, in sites other than the spine, in advanced cases leads to which of the following?

A. Bony ankylosis
B. Fibrous ankylosis (Correct Answer)
C. Loose joints
D. Charcot's joints

Explanation: **Explanation:** The hallmark of healing in **Tuberculous (TB) arthritis** of peripheral joints is **Fibrous Ankylosis**. **Why Fibrous Ankylosis is correct:** In tuberculosis, the infection is characterized by chronic granulomatous inflammation. Unlike pyogenic (septic) arthritis, TB bacilli do not produce proteolytic enzymes (like elastase or hyaluronidase) that completely destroy the articular cartilage. Instead, the cartilage is slowly replaced by **pannus** (granulation tissue). When the infection heals, this granulation tissue matures into dense fibrous tissue, leading to a "fibrous ankylosis"—where the joint becomes stiff but not completely fused by bone. **Analysis of Incorrect Options:** * **A. Bony Ankylosis:** This is the characteristic outcome of **Pyogenic/Septic Arthritis**. Proteolytic enzymes in pus destroy the cartilage entirely, allowing raw bone ends to meet and fuse. *Exception:* In TB, bony ankylosis occurs only in the **Spine (Pott’s disease)** and occasionally the sacroiliac joint. * **C. Loose Joints:** TB arthritis typically leads to stiffness and contractures, not laxity. Joint destruction and fibrosis limit movement. * **D. Charcot’s Joints:** This refers to neuropathic arthropathy (painless destruction) caused by loss of proprioception and pain sensation, commonly seen in Diabetes Mellitus, Syphilis (Tabes dorsalis), or Syringomyelia. **High-Yield NEET-PG Pearls:** * **Triple Deformity:** Classic in TB Knee (Flexion, Posterior subluxation, and External rotation). * **Phemister’s Triad (Radiology):** Juxta-articular osteopenia, peripheral osseous erosions, and gradual narrowing of joint space. * **Cold Abscess:** A collection of pus/debris without signs of inflammation (heat/redness), typical of TB. * **Gold Standard Diagnosis:** Synovial biopsy showing caseating granulomas.

Question 26: Acute osteomyelitis of long bones commonly affects which part?

A. Epiphysis
B. Diaphysis
C. Metaphysis (Correct Answer)
D. Articular surfaces

Explanation: ### Explanation **Correct Option: C. Metaphysis** Acute Hematogenous Osteomyelitis (AHO) most commonly affects the **metaphysis** of long bones due to its unique vascular anatomy. In children, the nutrient artery ends in **hairpin loops** of capillaries just below the growth plate. These loops lead into large, thin-walled venous sinusoids where blood flow becomes **sluggish and turbulent**. This stasis provides an ideal environment for circulating bacteria to settle, proliferate, and initiate infection. Additionally, the metaphyseal capillaries lack basement membranes (fenestrated), further facilitating bacterial transmigration. **Analysis of Incorrect Options:** * **A. Epiphysis:** The epiphysis is generally protected by the physis (growth plate), which acts as a mechanical and vascular barrier. It is only commonly involved in infants (under 1 year) where transphyseal vessels exist, or in cases of septic arthritis. * **B. Diaphysis:** While infection can spread to the diaphysis via the medullary canal or subperiosteal space, it is rarely the primary site of origin. An exception is **Syme’s/Ewing’s sarcoma** (a differential diagnosis) or infections in patients with **Sickle Cell Anemia** (often caused by *Salmonella*). * **D. Articular surfaces:** These are involved secondary to **Septic Arthritis**. While metaphyseal infection can rupture into a joint if the metaphysis is intracapsular (e.g., hip, shoulder, ankle), the primary site of bone infection remains the metaphysis. **High-Yield Clinical Pearls for NEET-PG:** 1. **Most common organism:** *Staphylococcus aureus* (overall). 2. **Sickle Cell Anemia:** *Salmonella* is a high-yield specific pathogen, though *S. aureus* remains common. 3. **Earliest X-ray sign:** Soft tissue swelling (seen at 3–5 days). Bony changes (rarefaction/periosteal reaction) take **10–14 days** to appear. 4. **Investigation of choice:** **MRI** (most sensitive for early diagnosis). 5. **Sequestrum:** Dead bone (radiodense); **Involucrum:** New bone formation around the sequestrum.

Question 27: All of the following findings are in favor of an inflammatory joint pathology except?

A. Juxta-articular osteoporosis
B. Non-uniform joint space loss (Correct Answer)
C. Bone erosions
D. Bilateral symmetric involvement

Explanation: ### Explanation The key to distinguishing joint pathologies lies in differentiating between **Inflammatory** (e.g., Rheumatoid Arthritis) and **Degenerative** (e.g., Osteoarthritis) processes. **Why "Non-uniform joint space loss" is the correct answer:** In **inflammatory arthritis**, the entire synovial membrane is inflamed (pannus formation), leading to the destruction of articular cartilage across the whole joint surface simultaneously. This results in **uniform/concentric joint space narrowing**. Conversely, **non-uniform (asymmetric) joint space loss** is a hallmark of **Osteoarthritis (Degenerative)**, where mechanical stress causes localized wear and tear (e.g., the medial compartment of the knee). **Analysis of Incorrect Options:** * **A. Juxta-articular osteoporosis:** Inflammatory cytokines (like TNF-α and IL-6) increase osteoclast activity in the bone adjacent to the inflamed synovium. This "near-joint" bone thinning is a classic early sign of Rheumatoid Arthritis (RA). * **C. Bone erosions:** The pannus in inflammatory conditions invades the "bare areas" of the bone (where the capsule attaches but cartilage is absent), leading to marginal erosions. * **D. Bilateral symmetric involvement:** Systemic inflammatory conditions (like RA) typically present with a symmetrical distribution, unlike the often asymmetrical or weight-bearing distribution of degenerative diseases. **High-Yield Clinical Pearls for NEET-PG:** * **Radiological Hallmarks of Osteoarthritis (Degenerative):** LOSS — **L**oss of joint space (non-uniform), **O**steophytes, **S**ubchondral sclerosis, and **S**ubchondral cysts. * **Radiological Hallmarks of Rheumatoid Arthritis (Inflammatory):** Soft tissue swelling, Juxta-articular osteopenia, Uniform joint space narrowing, and Marginal erosions. * **Joint Aspiration:** Inflammatory fluids have high WBC counts (>2,000 cells/mm³) and poor mucin clot tests, whereas degenerative fluids are clear and viscous.

Question 28: What is the most common site of tuberculosis?

A. Hip joint
B. Spine (Correct Answer)
C. Knee joint
D. Ankle joint

Explanation: **Explanation:** Tuberculosis (TB) of the musculoskeletal system accounts for approximately 1–3% of all TB cases and about 10% of extrapulmonary TB cases. Among these, the **Spine (Pott’s disease)** is the most common site, representing roughly **50% of all osteoarticular tuberculosis** cases. **Why Spine is the Correct Answer:** The spine is highly susceptible due to the rich vascular supply of the vertebral bodies and the presence of the **Batson’s venous plexus**, which allows for the hematogenous spread of *Mycobacterium tuberculosis* from primary sites (usually the lungs or lymph nodes). The infection typically begins in the anterior part of the vertebral body near the disc space (paradiscal lesion). **Analysis of Incorrect Options:** * **Hip Joint (Option A):** This is the **second most common** site of osteoarticular TB (approx. 15%). It usually presents with a "wandering acetabulum" or pathological dislocation in advanced stages. * **Knee Joint (Option B):** This is the **third most common** site. It often presents with "triple deformity" (flexion, posterior subluxation, and external rotation of the tibia). * **Ankle Joint (Option D):** While TB can affect any joint, the ankle and foot are significantly less common than the spine, hip, or knee. **NEET-PG High-Yield Pearls:** * **Most common site in Spine:** Lower Thoracic and Upper Lumbar vertebrae. * **Earliest sign on X-ray:** Rarefaction/demineralization of the bone and narrowing of the disc space. * **Phemister’s Triad (Radiological features of TB joints):** 1. Juxta-articular osteoporosis, 2. Peripherally located osseous erosions, 3. Gradual narrowing of the joint space. * **Cold Abscess:** A hallmark of spinal TB, it occurs when the infection tracks along tissue planes (e.g., Psoas abscess) without the typical signs of acute inflammation (heat/redness).

Question 29: Brodie's abscess occurs in which type of bone?

A. Flat bone
B. Small bone
C. Long bone (Correct Answer)
D. Sesamoid bone

Explanation: **Explanation:** **Brodie’s abscess** is a localized, chronic form of pyogenic osteomyelitis. It is characterized by a collection of pus surrounded by a wall of granulation tissue and reactive bone (sclerosis). **Why Long Bone is Correct:** Brodie’s abscess typically occurs in the **metaphysis of long bones**, with the **tibia** (distal or proximal) being the most common site, followed by the femur. The metaphysis is the preferred site because of its high vascularity and the presence of "hairpin" loops of capillary beds, which allow blood-borne bacteria (most commonly *Staphylococcus aureus*) to settle and form a localized infection. Because the patient’s immunity is relatively high or the organism’s virulence is low, the body walls off the infection rather than allowing it to spread. **Why Other Options are Incorrect:** * **Flat bones & Small bones:** While osteomyelitis can occur in these bones (e.g., pelvis or tarsals), they lack the specific metaphyseal anatomy and vascular patterns that typically lead to the formation of a classic Brodie’s abscess. * **Sesamoid bones:** These bones (like the patella) are embedded in tendons and have a limited blood supply; they are extremely rare sites for any form of primary osteomyelitis. **High-Yield Clinical Pearls for NEET-PG:** * **Most common organism:** *Staphylococcus aureus*. * **Classic X-ray finding:** A well-defined **radiolucent (lytic) lesion** in the metaphysis surrounded by a rim of **sclerotic bone**. * **Clinical presentation:** Chronic, intermittent pain (often worse at night) and localized tenderness, usually without systemic symptoms like fever. * **Differential Diagnosis:** Often confused with **Osteoid Osteoma**; however, the pain in Brodie’s abscess is not always relieved by aspirin, unlike Osteoid Osteoma. * **Treatment:** Surgical curettage and antibiotics.

Question 30: The joint commonly involved in psoriatic arthritis is?

A. Hip
B. Shoulder
C. Wrist
D. Knee (Correct Answer)

Explanation: **Explanation:** Psoriatic arthritis (PsA) is a chronic inflammatory spondyloarthropathy associated with psoriasis. While PsA is famous for involving the small joints of the hands (specifically the Distal Interphalangeal joints), when considering **large joints**, the **Knee** is the most commonly affected joint. 1. **Why Knee is Correct:** Psoriatic arthritis frequently presents as an asymmetrical oligoarthritis (affecting <5 joints). In this clinical subtype, the knee is the most frequent large joint involved. It often presents with significant effusion and inflammatory markers. 2. **Why other options are incorrect:** * **Hip and Shoulder:** While these proximal girdle joints can be involved in the symmetric polyarthritis or spondylitic subtypes of PsA, they are significantly less common than the knee. Hip involvement, in particular, is more characteristic of Ankylosing Spondylitis. * **Wrist:** Although the wrist is often involved in the symmetric polyarthritis subtype (which mimics Rheumatoid Arthritis), the knee remains statistically more prevalent across the various clinical presentations of PsA. **High-Yield Clinical Pearls for NEET-PG:** * **Classic Sign:** **DIP joint involvement** is a hallmark of PsA (unlike RA, which spares the DIP). * **Dactylitis:** "Sausage digit" (diffuse swelling of a finger or toe) is a pathognomonic feature. * **Radiology:** Look for the **"Pencil-in-cup" deformity** (erosion of the distal bone with expansion of the proximal base). * **Nail Changes:** Pitting of nails and onycholysis are strong clinical predictors of joint involvement. * **Mnemonic:** PsA is **Seronegative** (RF negative).

Practice by Chapter

Septic Arthritis

Practice Questions

Osteomyelitis

Practice Questions

Tuberculosis of Bones and Joints

Practice Questions

Fungal and Parasitic Infections

Practice Questions

Diabetic Foot Infections

Practice Questions

Prosthetic Joint Infections

Practice Questions

Reactive Arthritis

Practice Questions

Management of Joint Infections

Practice Questions

Prevention of Orthopaedic Infections

Practice Questions

Biofilms in Orthopaedic Infections

Practice Questions

Antibiotic Prophylaxis

Practice Questions

Implant-Related Infections

Practice Questions

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