Arthrology and Infections — MCQs

Arthrology and Infections Indian Medical PG Practice Questions and MCQs

Question 131: In rheumatoid arthritis, where does the pathology typically begin?

A. Articular cartilage
B. Capsule
C. Synovium (Correct Answer)
D. Muscles

Explanation: **Explanation:** **Rheumatoid Arthritis (RA)** is a chronic, systemic autoimmune inflammatory disorder. The primary site of pathology is the **Synovium**. 1. **Why Synovium is correct:** The disease process begins as **Synovitis**. Autoantibodies (like Rheumatoid Factor and Anti-CCP) trigger an inflammatory cascade within the synovial membrane. This leads to synovial hypertrophy and the formation of **Pannus**—a vascular, inflammatory granulation tissue. This pannus eventually invades and destroys the underlying bone and cartilage. 2. **Why other options are incorrect:** * **Articular Cartilage:** This is the primary site of pathology in **Osteoarthritis (OA)**, which is a degenerative "wear and tear" process. In RA, cartilage destruction is secondary to synovial inflammation. * **Capsule:** While the joint capsule becomes thickened and fibrotic in late-stage RA (leading to contractures), it is not the initiating site. * **Muscles:** Muscle wasting (atrophy) is a common secondary feature of RA due to disuse and cytokine-mediated inflammation, but the pathology does not originate here. **High-Yield Clinical Pearls for NEET-PG:** * **Earliest Sign:** The earliest radiological sign of RA is **Peri-articular soft tissue swelling**, followed by **Peri-articular osteopenia** (juxta-articular rarefaction). * **Joint Involvement:** RA typically affects small joints of the hands and feet (MCP, PIP, MTP) but characteristically **spares the Distal Interphalangeal (DIP) joints**. * **Pannus:** This is the hallmark of RA; it consists of inflammatory cells (T-cells, plasma cells), neovascularization, and fibroblasts. * **Serology:** Anti-CCP (Cyclic Citrullinated Peptide) is the **most specific** marker for RA.

Question 132: A 30-year-old patient presents with radiographic findings of endosteal bone formation and sclerosed bone. What is the likely diagnosis?

A. Garre's Osteomyelitis
B. Chronic focal sclerosing Osteomyelitis (Correct Answer)
C. Acute Osteomyelitis
D. Chronic Osteomyelitis

Explanation: ### Explanation The correct diagnosis is **Chronic Focal Sclerosing Osteomyelitis** (also known as Condensing Osteitis). **1. Why the Correct Answer is Right:** Chronic focal sclerosing osteomyelitis is a tissue reaction to a low-grade, chronic inflammatory stimulus (usually at the apex of a tooth or in long bones). The hallmark of this condition is a **proliferative bone response** rather than bone destruction. Radiographically, it presents as a well-defined radiopaque mass characterized by **endosteal bone formation** and **increased bone density (sclerosis)**. Unlike other forms of osteomyelitis, there is typically no sequestration or suppuration. **2. Why the Other Options are Wrong:** * **Garre’s Osteomyelitis (Chronic Osteomyelitis with Proliferative Periostitis):** While it involves bone formation, it is characterized by **periosteal** reaction (onion-skin appearance) rather than primary endosteal sclerosis. It typically occurs in children and young adults involving the mandible. * **Acute Osteomyelitis:** This is characterized by rapid bone destruction, systemic symptoms (fever, chills), and soft tissue swelling. Radiographic changes (like the involucrum) take 10–14 days to appear and are destructive, not purely sclerotic. * **Chronic Osteomyelitis:** This typically presents with the classic triad of **Sequestrum** (dead bone), **Involucrum** (new bone sheath), and **Cloaca** (opening for pus). It is a mix of bone destruction and formation, not isolated focal sclerosis. **3. NEET-PG High-Yield Pearls:** * **Garre’s Osteomyelitis:** Look for the "Onion-skin" periosteal reaction on X-ray. * **Brodie’s Abscess:** A form of chronic osteomyelitis presenting as a radiolucent lesion with a sclerotic rim, usually in the metaphysis. * **Sclerotic Bone:** Always differentiate between endosteal (inside) and periosteal (outside) bone formation to narrow down the type of osteomyelitis.

Question 133: Which of the following is NOT true about synovial chondromatosis?

A. Snow storm appearance of joint
B. Most common cause of loose bodies in joint (Correct Answer)
C. Most common in knee joint
D. Trauma can lead to synovial chondromatosis

Explanation: ### Explanation **Synovial Chondromatosis** is a benign, idiopathic condition characterized by the metaplasia of the synovium into chondrocytes, leading to the formation of multiple cartilaginous loose bodies within the joint space. **Why Option B is the Correct Answer (The False Statement):** While synovial chondromatosis is a well-known cause of loose bodies, it is **not the most common cause**. The most common cause of loose bodies in a joint is **Osteoarthritis** (due to detached osteophytes) or **Trauma**. In younger populations, **Osteochondritis Dissecans** is also a more frequent cause than synovial chondromatosis. **Analysis of Other Options:** * **Option A (Snow storm appearance):** This is a classic radiological description. When the cartilaginous bodies calcify (synovial osteochondromatosis), multiple small, radio-opaque loose bodies of similar size and shape create a "snow storm" or "rice grain" appearance on X-ray. * **Option C (Most common in knee joint):** This is true. The knee is the most frequently affected site (up to 70% of cases), followed by the hip, shoulder, and elbow. It is typically monoarticular. * **Option D (Trauma):** While the primary form is idiopathic, **Secondary Synovial Chondromatosis** can be triggered by joint trauma, mechanical stress, or underlying degenerative joint disease. **Clinical Pearls for NEET-PG:** * **Milgram’s Classification:** Used to stage the disease (Stage I: Active intrasynovial disease; Stage II: Transitional; Stage III: Multiple free osteochondral bodies). * **Clinical Presentation:** Joint pain, swelling, and "locking" of the joint. * **Treatment:** Surgical removal of loose bodies and **synovectomy** (to prevent recurrence). * **Pathology:** Characterized by "cartilage nests" within the synovial membrane.

Question 134: Multifocal non-suppurative osteomyelitis is seen in which of the following conditions?

A. Infantile cortical hyperostosis
B. Thalassemia
C. Salmonella infections
D. SAPHO syndrome (Correct Answer)

Explanation: **Explanation:** **SAPHO syndrome** is the correct answer because it is a rare inflammatory disorder characterized by **sterile (non-suppurative)** bone and joint inflammation. The acronym stands for **S**ynovitis, **A**cne, **P**ustulosis, **H**yperostosis, and **O**steitis. The hallmark pathological feature is chronic recurrent multifocal osteomyelitis (CRMO), which involves inflammatory bone lesions without the presence of pyogenic bacteria or pus formation. **Analysis of Incorrect Options:** * **Infantile cortical hyperostosis (Caffey’s Disease):** While it involves multifocal bone formation (hyperostosis) and subperiosteal new bone, it is characterized by sudden onset irritability and soft tissue swelling in infants, typically involving the mandible. It is a proliferative bone disease rather than a classic "osteomyelitis" pattern. * **Thalassemia:** This is a hematologic disorder. Bone changes (like the "crew-cut" appearance) occur due to **extramedullary hematopoiesis** and marrow expansion, not due to an inflammatory or non-suppurative osteomyelitic process. * **Salmonella infections:** This causes **suppurative** (pus-forming) osteomyelitis. It is classically associated with Sickle Cell Anemia. Since the question specifies "non-suppurative," this option is incorrect. **Clinical Pearls for NEET-PG:** * **SAPHO Syndrome:** Look for the "Bull’s head" sign on a bone scan (increased uptake at the sternoclavicular joints). * **CRMO:** This is considered the pediatric equivalent or a component of the SAPHO spectrum. * **Treatment:** First-line treatment typically involves NSAIDs; bisphosphonates or TNF-alpha inhibitors are used for refractory cases. * **Garré’s Sclerosing Osteomyelitis:** Another form of non-suppurative osteomyelitis, but it is typically unifocal (usually the mandible) and associated with dental infections.

Question 135: What is the most common site of tuberculosis?

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

Explanation: **Explanation:** **Tuberculosis (TB) of the musculoskeletal system** accounts for approximately 1–3% of all TB cases and about 10–15% of all extrapulmonary TB cases. **1. Why Spine is the Correct Answer:** The **Spine (Pott’s Disease)** is the most common site of skeletal tuberculosis, accounting for approximately **50%** of all osteoarticular TB cases. The infection typically involves the paradiscal region of the vertebral bodies. The high incidence is attributed to the rich vascular supply (Batson’s venous plexus) which allows for the hematogenous spread of *Mycobacterium tuberculosis* from a primary focus (usually the lungs or lymph nodes). **2. Analysis of Incorrect Options:** * **Hip (Option C):** This is the **second most common** site of skeletal TB (roughly 15%). It is the most common site in the extremities. * **Knee (Option B):** This is the **third most common** site. Like the hip, it is a weight-bearing joint, making it more susceptible than upper limb joints. * **Shoulder (Option D):** TB of the shoulder (often presenting as *Caries Sicca*) is relatively rare compared to the weight-bearing joints of the lower limb and the spine. **3. NEET-PG High-Yield Pearls:** * **Most common site in Spine:** Lower Thoracic and Upper Lumbar vertebrae. * **Most common type of vertebral involvement:** Paradiscal (leads to disc space narrowing). * **Cold Abscess:** A hallmark of skeletal TB; it lacks the typical signs of inflammation (heat/redness). * **Order of frequency:** Spine > Hip > Knee > Elbow > Shoulder. * **Diagnosis:** Gold standard is tissue biopsy for histopathology (granulomas) and Culture (Lowenstein-Jensen medium) or GeneXpert.

Question 136: What is the most common cause of non-gonococcal septic arthritis?

A. Staphylococcus aureus (Correct Answer)
B. Haemophilus influenzae
C. Streptococcus pyogenes
D. Streptococcus pneumoniae

Explanation: **Explanation:** **Staphylococcus aureus (Option A)** is the most common cause of non-gonococcal septic arthritis across all age groups, including adults and children. It is a highly virulent organism that typically reaches the joint via hematogenous spread. Its ability to produce various toxins and enzymes (like protein A and adhesins) allows it to adhere to the synovial membrane and cause rapid joint destruction. **Analysis of Incorrect Options:** * **Haemophilus influenzae (Option B):** Historically, this was the leading cause in children under 2 years of age. However, since the introduction of the **Hib vaccine**, its incidence has drastically declined, making *S. aureus* the most common cause in this age group as well. * **Streptococcus pyogenes (Option C):** This is the second most common cause in healthy adults and is frequently associated with skin infections or trauma, but it lags significantly behind *S. aureus*. * **Streptococcus pneumoniae (Option D):** While it can cause septic arthritis, it is much less common and usually occurs secondary to pneumonia or meningitis. **High-Yield Clinical Pearls for NEET-PG:** 1. **Most common joint involved:** The **Knee** joint (followed by the hip). 2. **Route of infection:** Hematogenous spread is the most common route. 3. **Special Populations:** * **Sickle Cell Anemia:** *Salmonella* is a characteristic (though *S. aureus* remains common). * **IV Drug Users:** High incidence of *Pseudomonas aeruginosa* (often involving the sternoclavicular or sacroiliac joints). * **Sexually Active Young Adults:** *Neisseria gonorrhoeae* is the most common cause of *gonococcal* arthritis (presents with migratory polyarthralgia and tenosynovitis). 4. **Gold Standard Diagnosis:** Arthrocentesis with synovial fluid analysis (WBC count typically >50,000/mm³).

Question 137: What is true about synovial chondromatosis?

A. Elderly men are typically affected.
B. Bone scan is usually normal.
C. Metaplastic cartilage formation occurs throughout the synovium. (Correct Answer)
D. Chondrosarcoma is a common complication.

Explanation: **Synovial Chondromatosis** (also known as Reichel’s syndrome) is a benign monoarticular disorder characterized by the development of multiple cartilaginous nodules within the joint space. ### **Explanation of the Correct Option** **Option C is correct** because the primary pathology is **cartilaginous metaplasia** of the subsynovial connective tissue. The synovium undergoes a transformation where it produces small nodules of hyaline cartilage. These nodules can eventually pedunculate, break free, and become "loose bodies" (joint mice) within the joint cavity. ### **Why Other Options are Incorrect** * **Option A:** It typically affects **young to middle-aged adults** (20–50 years), not the elderly. There is a male predominance (2:1 ratio). * **Option B:** A **Bone Scan** usually shows **increased uptake** (hot scan) due to active metabolic activity and calcification within the synovium and loose bodies. * **Option D:** Malignant transformation to **Chondrosarcoma is rare** (<5% of cases). It is generally considered a benign, though locally aggressive, condition. ### **High-Yield Clinical Pearls for NEET-PG** * **Most Common Site:** The **Knee joint** is affected in >50% of cases, followed by the hip and elbow. * **Radiological Feature:** Characterized by multiple "snowstorm" appearances or "apple-core" lesions if the femoral neck is involved. * **Milgram’s Classification:** 1. **Phase I (Early):** Active intrasynovial disease; no loose bodies. 2. **Phase II (Transitional):** Active intrasynovial disease with free-floating loose bodies. 3. **Phase III (Late):** Multiple loose bodies; quiescent synovium. * **Treatment of Choice:** Arthroscopic or open **synovectomy** with removal of loose bodies. Recurrence is common if the synovectomy is incomplete.

Question 138: Which part of the bone is most commonly affected in children with acute osteomyelitis?

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

Explanation: **Explanation:** Acute Hematogenous Osteomyelitis (AHO) is primarily a disease of growing children, and the **Metaphysis** is the most common site of involvement due to its unique vascular anatomy. **Why Metaphysis is the correct answer:** 1. **Hairpin Loops:** The nutrient arteries end in sharp "hairpin" loops at the physeal plate before emptying into large venous sinusoids. This sudden change in direction causes turbulent blood flow and stasis. 2. **Sluggish Blood Flow:** The slow flow in the venous sinusoids allows circulating bacteria (most commonly *Staphylococcus aureus*) to settle and proliferate. 3. **Deficient Phagocytosis:** The capillary loops in this region lack a robust population of functional phagocytic cells (macrophages), making it an ideal environment for infection to take hold. **Why other options are incorrect:** * **Diaphysis:** While it can be involved (e.g., in Sickle Cell Anemia where *Salmonella* is common), it lacks the sluggish venous sinusoids found in the metaphysis. * **Epiphysis:** This is usually spared because the physis (growth plate) acts as a mechanical barrier to the spread of infection. However, in infants (<1 year), transphyseal vessels exist, allowing infection to reach the epiphysis and joint. * **Vertebrae:** This is the most common site for osteomyelitis in **adults**, not children. **High-Yield Clinical Pearls for NEET-PG:** * **Most common organism:** *Staphylococcus aureus* (overall). * **Most common site:** Distal Femur > Proximal Tibia (areas of rapid growth). * **Earliest X-ray sign:** Soft tissue swelling (bone changes like periosteal reaction take 7–14 days to appear). * **Investigation of choice:** **MRI** (most sensitive for early detection). * **Sequestrum:** Dead bone (radiodense); **Involucrum:** New bone formation around the sequestrum.

Question 139: A 62-year-old diabetic patient presents with burning pain of the right foot, which began 3 weeks after an inversion injury of the ankle. Examination reveals flat arches and decreased proprioception bilaterally. What is the most likely diagnosis?

A. Acromegaly
B. Hemochromatosis
C. Hemophilia
D. Charcot arthropathy (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. Charcot arthropathy** **Concept:** Charcot arthropathy (Neuropathic Osteoarthropathy) is a progressive degenerative condition affecting joints in patients with **sensory neuropathy**. The most common cause today is **Diabetes Mellitus**. The pathophysiology involves a "loss of protective sensation" (decreased proprioception and pain), leading to repetitive microtrauma. This triggers a massive inflammatory response, bone resorption, and eventual joint collapse (e.g., "rocker-bottom foot" or flat arches). In this case, the **minor trauma (inversion injury)** acted as the inciting event in a patient with pre-existing diabetic neuropathy. **Why other options are incorrect:** * **A. Acromegaly:** While it causes joint pain due to cartilage overgrowth and secondary osteoarthritis, it typically presents with "spade-like hands," jaw protrusion, and organomegaly, rather than acute post-traumatic collapse. * **B. Hemochromatosis:** Classically involves the 2nd and 3rd metacarpophalangeal (MCP) joints with characteristic "hook-like" osteophytes. It does not typically present with acute neuropathic collapse after trauma. * **C. Hemophilia:** Causes "Hemophilic Arthropathy" due to recurrent intra-articular bleeds (hemarthrosis), most commonly affecting the **knee**. It is a disease of younger patients with clotting factor deficiencies, not elderly diabetics. **NEET-PG High-Yield Pearls:** * **Most common site:** Midfoot (Tarsometatarsal/Lisfranc joints). * **Clinical Clue:** A "warm, swollen, red foot" in a diabetic that mimics cellulitis but lacks systemic signs of infection (fever/elevated WBC). * **Radiology:** Look for the **"6 Ds"**: Distended joint, Density increase (sclerosis), Debris, Disorganization, Dislocation, and Destruction. * **Management:** Gold standard for the acute phase is **Total Contact Casting (TCC)** to offload the limb.

Question 140: Which is the most sensitive investigation for early bone infections?

A. X-ray
B. CT scan
C. Bone scan (Correct Answer)
D. USG

Explanation: ### Explanation **Correct Option: C. Bone scan** The bone scan (specifically the **Technetium-99m MDP scan**) is the most sensitive investigation for early bone infections like acute osteomyelitis. It can detect changes in bone metabolism and increased vascularity within **24 to 48 hours** of the onset of infection. It works by identifying "hot spots" where there is increased osteoblastic activity and blood flow, long before structural changes are visible on conventional imaging. **Why other options are incorrect:** * **A. X-ray:** This is the least sensitive early investigation. Radiographic changes (like periosteal reaction or bone destruction) only become visible after **30–50% of bone mineral content** is lost, which typically takes **10–14 days**. * **B. CT scan:** While excellent for viewing cortical bone detail, sequestrum (dead bone), and gas within the bone, it is not as sensitive as a bone scan for detecting the initial inflammatory phase of early infection. * **D. USG:** Ultrasound is useful for detecting **subperiosteal abscesses** or joint effusions in pediatric cases, but it cannot visualize the intramedullary infection itself. **Clinical Pearls for NEET-PG:** * **Gold Standard/Most Sensitive Overall:** While Bone Scan is the most sensitive among the given options, **MRI** is considered the most sensitive and specific imaging modality overall for early osteomyelitis (detecting marrow edema within hours). * **Triple Phase Bone Scan:** In osteomyelitis, all three phases (Blood flow, Blood pool, and Delayed skeletal phase) show increased uptake. * **Cold Scan:** In very early stages or in cases of neonatal osteomyelitis where blood supply is compromised, a bone scan may paradoxically show a "cold spot." * **Definitive Diagnosis:** The gold standard for diagnosis remains **bone aspiration/biopsy** and culture.

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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