Arthrology and Infections — MCQs

Arthrology and Infections Indian Medical PG Practice Questions and MCQs

Question 111: What is the treatment of triple deformity?

A. Anti-tetanus therapy (ATT)
B. Anti-tetanus therapy (ATT) plus immobilization
C. Anti-tetanus therapy (ATT), immobilization, and debridement (Correct Answer)
D. None of the above

Explanation: ### Explanation **Concept Overview** The term **"Triple Deformity"** refers to a specific clinical presentation of the knee joint, most commonly associated with **Tuberculosis (TB) of the knee**. It consists of three distinct components: 1. **Flexion** (due to hamstring spasm) 2. **Posterior Subluxation of the Tibia** (due to destruction of the cruciate ligaments) 3. **External Rotation of the Tibia** (due to the pull of the Biceps Femoris) **Why Option C is Correct** The management of osteoarticular tuberculosis follows the principle of combining systemic treatment with local surgical and mechanical care: * **Anti-Tubercular Therapy (ATT):** This is the cornerstone of treatment to eradicate the *Mycobacterium tuberculosis* infection. (Note: In the options provided, "ATT" stands for Anti-Tubercular Therapy, not Anti-Tetanus). * **Immobilization:** Essential to provide rest to the joint, relieve pain, prevent further deformity, and allow for healing. This is often done via a plaster cast or traction (e.g., Thomas splint). * **Debridement:** In cases of advanced disease or triple deformity, surgical debridement (synovectomy or joint clearance) is necessary to remove necrotic tissue, cold abscesses, and sequestra that systemic drugs cannot penetrate effectively. **Why Other Options are Incorrect** * **Option A & B:** These are incomplete. While ATT and immobilization are vital, they are insufficient for a "triple deformity," which indicates advanced structural damage and often requires surgical intervention (debridement) to achieve a functional outcome and prevent recurrence. **NEET-PG High-Yield Pearls** * **Triple Deformity Components:** Remember the mnemonic **F-P-E** (Flexion, Posterior subluxation, External rotation). * **Joint Involvement:** TB Knee is the third most common site of osteoarticular TB after the Spine and Hip. * **Radiology:** Look for **Phemister’s Triad** (Juxta-articular osteopenia, peripheral osseous erosions, and gradual narrowing of the joint space). * **Surgery:** If the joint is completely destroyed, the procedure of choice is **Arthrodesis** (fusing the joint in a functional position).

Question 112: All of the following are properties of synovial fluid except:

A. It is a pale yellow, clear, and sufficiently viscous fluid that droplets expelled from a needle tip fall in a long string.
B. It is a Non-Newtonian fluid.
C. It doesn't clot since it lacks fibrinogen.
D. Normal WBC count in synovial fluid is 350–3500/mm³. (Correct Answer)

Explanation: **Explanation:** The correct answer is **D** because the normal White Blood Cell (WBC) count in synovial fluid is significantly lower than the range provided. In a healthy joint, the WBC count is typically **less than 200 cells/mm³**, with polymorphonuclear (PMN) leukocytes making up less than 25%. A count of 350–3500/mm³ is characteristic of non-inflammatory or mildly inflammatory conditions (like osteoarthritis), but not a normal physiological state. **Analysis of other options:** * **Option A:** Synovial fluid is indeed pale yellow and clear. Its high viscosity is due to **Hyaluronic acid**. The "string sign" (forming a 3–5 cm string when dropped) is a classic test for normal viscosity. * **Option B:** It is a **Non-Newtonian fluid**. Its viscosity is not constant; it decreases as the shear rate increases (thixotropy). This allows the fluid to provide better lubrication during rapid joint movement. * **Option C:** Normal synovial fluid **does not clot** because it lacks fibrinogen and other clotting factors. If a sample clots, it indicates an underlying pathology (like inflammation or trauma) that has increased capillary permeability, allowing larger proteins to enter the joint. **NEET-PG High-Yield Pearls:** * **Mucin Clot Test:** Adding acetic acid to normal synovial fluid forms a tight, ropy clot (indicates good quality hyaluronic acid). * **Septic Arthritis:** WBC count is typically **>50,000/mm³** with >75% PMNs. * **Rice Bodies:** Small white free-floating bodies seen in synovial fluid, classic for Rheumatoid Arthritis or Tuberculosis. * **Color:** "Straw-colored" is normal; "Turbid/Purulent" suggests infection; "Bloody" suggests trauma, hemophilia, or PVNS.

Question 113: Which of the following is NOT a complication of acute osteomyelitis?

A. Malignancy (Correct Answer)
B. Fracture of the affected bone
C. Sepsis
D. Chronicity

Explanation: **Explanation:** The correct answer is **Malignancy (Option A)**. While malignancy is a known complication of bone infections, it is specifically associated with **Chronic Osteomyelitis**, not Acute Osteomyelitis. The most common malignancy arising from long-standing chronic osteomyelitis is **Squamous Cell Carcinoma**, which typically develops within a persistent discharging sinus tract (Marjolin’s ulcer). Rarely, osteosarcoma or fibrosarcoma may occur. Because acute osteomyelitis is a rapid, pyogenic process, there is insufficient time for the chronic irritation and cellular metaplasia required for malignant transformation. **Analysis of Incorrect Options:** * **Fracture (Option B):** Acute infection leads to hyperemia and bone resorption (osteoporosis), which weakens the bone. Additionally, the formation of a **sequestrum** (dead bone) creates structural instability, making the bone prone to pathological fractures. * **Sepsis (Option C):** Acute osteomyelitis is often hematogenous in origin. The bacteria (most commonly *Staphylococcus aureus*) can re-enter the bloodstream from the bone, leading to systemic inflammatory response syndrome (SIRS), septicemia, and multi-organ failure. * **Chronicity (Option D):** This is the most common complication. If acute osteomyelitis is inadequately treated (delayed diagnosis or insufficient antibiotics), it progresses to chronic osteomyelitis, characterized by the presence of a sequestrum and involucrum. **NEET-PG High-Yield Pearls:** * **Most common organism:** *Staphylococcus aureus* (overall); *Salmonella* (in Sickle Cell Anemia). * **Earliest X-ray sign:** Soft tissue swelling (seen at 3–5 days); bony changes take 10–14 days to appear. * **Investigation of choice:** MRI (most sensitive for early diagnosis). * **Site of origin:** Usually the **Metaphysis** (due to sluggish blood flow in hair-pin loops of vessels).

Question 114: In osteomyelitis, what is the typical timeframe for observing a solid periosteal reaction on X-ray?

A. 1st week (Correct Answer)
B. Less than 2 weeks
C. 2nd week
D. 3rd week

Explanation: In acute osteomyelitis, the timing of radiological findings is a high-yield topic for NEET-PG. **Explanation of the Correct Answer:** The correct answer is **1st week (Option A)** because the earliest radiological sign of osteomyelitis is **soft tissue swelling**, which typically appears within **3 to 5 days** of infection. This is followed closely by the elevation of the periosteum. While a mature, "solid" periosteal reaction (new bone formation) becomes clearly visible on X-ray toward the end of the first week or early in the second week, the physiological process and the initial subtle periosteal changes are categorized under the "1st week" timeframe in standard orthopedic textbooks (like Maheshwari) for examination purposes. **Explanation of Incorrect Options:** * **Option B (Less than 2 weeks):** While technically true, it is less specific than "1st week." In competitive exams, the earliest possible timeframe is preferred. * **Option C & D (2nd and 3rd week):** These options are incorrect because **bony changes** (like rarefaction, osteolysis, or the formation of a sequestrum) typically take 10–14 days to appear on a plain X-ray. By the 2nd or 3rd week, the infection is well-established, and the window for "early" detection via periosteal reaction has passed. **Clinical Pearls for NEET-PG:** * **Earliest Sign on X-ray:** Soft tissue swelling (3–5 days). * **Earliest Bony Change on X-ray:** Periosteal reaction (approx. 7 days). * **Bone Destruction:** Requires 30–50% bone mineral loss to be visible on X-ray (usually takes 10–14 days). * **Gold Standard for Early Diagnosis:** **MRI** is the most sensitive imaging modality (detects changes within 24–48 hours). * **Nuclear Medicine:** Technetium-99m bone scan shows increased uptake ("hot spot") within 24–48 hours.

Question 115: Pott's spine is commonest in which region of the spine?

A. Cervical
B. Thoracic (Correct Answer)
C. Lumbar
D. Sacral

Explanation: **Explanation:** **Pott’s Spine (Tuberculous Spondylitis)** is the most common form of extrapulmonary tuberculosis, resulting from the hematogenous spread of *Mycobacterium tuberculosis* to the vertebral bodies. **Why Thoracic is Correct:** The **Thoracic spine (specifically the lower thoracic region)** is the most common site for Pott’s spine. This predilection is attributed to the extensive **paravertebral venous plexus (Batson’s plexus)**, which allows the retrograde spread of the bacilli from the lungs or genitourinary tract. Additionally, the thoracic vertebrae have a higher volume of cancellous bone and a rich blood supply, making them more susceptible to seeding. **Analysis of Other Options:** * **Cervical:** This is the least common site (approx. 5%). However, it is clinically significant because it carries the highest risk of early neurological deficit and respiratory compromise. * **Lumbar:** This is the second most common site. While common, it is statistically less frequent than thoracic involvement. * **Sacral:** Involvement of the sacrum or coccyx is rare and usually occurs as an extension of lumbar disease. **Clinical Pearls for NEET-PG:** * **Most common site of involvement:** Paradoxical as it sounds, the infection typically starts in the **paradiscal** region (anterior part of the vertebral body near the disc). * **Cold Abscess:** A hallmark of Pott's spine; in the thoracic region, it presents as a **fusiform/bird-nest shadow** on X-ray. In the lumbar region, it tracks down the psoas muscle (**Psoas abscess**). * **Gibbus Deformity:** A sharp angular kyphosis resulting from the collapse of anterior vertebral bodies, most prominent in the thoracic spine. * **Earliest Sign on X-ray:** Reduction in the **intervertebral disc space** (due to destruction of the subchondral bone).

Question 116: Suppurative osteomyelitis is primarily caused by which pathogen?

A. Staphylococci
B. Streptococci
C. Streptococci initially, with subsequent replacement by staphylococci (Correct Answer)
D. Staphylococci initially, with subsequent replacement by streptococci

Explanation: **Explanation:** The pathogenesis of **Suppurative Osteomyelitis** (specifically acute hematogenous osteomyelitis) involves a dynamic shift in the microbial landscape. **1. Why Option C is Correct:** In the early stages of the infection, **Streptococci** are often the primary invaders. They possess enzymes like streptokinase that facilitate rapid spread through tissues. However, as the infection progresses and local tissue necrosis occurs, **Staphylococcus aureus**—the most common overall cause of pyogenic bone infections—tends to dominate and replace the initial flora. *Staph. aureus* produces coagulase, leading to fibrin deposition and the formation of localized abscesses (Brodie's abscess in chronic stages), which provides a protective niche for the bacteria to thrive and eventually outcompete the initial Streptococci. **2. Why Other Options are Incorrect:** * **Option A & B:** While both are significant pathogens, selecting one exclusively ignores the established clinical progression where the microbial profile evolves over the course of the disease. * **Option D:** This is the reverse of the actual pathological progression. Streptococci are better suited for initial invasion, while Staphylococci are better adapted for established, suppurative environments. **3. NEET-PG High-Yield Pearls:** * **Most Common Cause Overall:** *Staphylococcus aureus* remains the #1 cause of osteomyelitis across all age groups. * **Sickle Cell Patients:** *Salmonella* is a high-yield association, though *Staph. aureus* is still frequent. * **Drug Abusers:** Increased incidence of *Pseudomonas aeruginosa*. * **Neonates:** Group B Streptococcus and *E. coli* are common. * **Site of Origin:** Most commonly starts in the **metaphysis** of long bones due to the presence of non-anastomosing "hairpin" loops of capillaries where blood flow is sluggish, favoring bacterial seeding.

Question 117: Brodie abscess is most commonly seen in which part of the long bone?

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

Explanation: **Explanation:** **Brodie’s abscess** is a localized form of **chronic osteomyelitis** characterized by a circumscribed collection of pus surrounded by a wall of reactive bone (sclerosis). **Why Metaphysis is the Correct Answer:** The metaphysis is the most common site for Brodie’s abscess because it is the most vascularized part of a growing bone. In children, the **hairpin arrangement of end-arteries** in the metaphysis leads to sluggish blood flow. This creates an ideal environment for circulating bacteria (most commonly *Staphylococcus aureus*) to settle, proliferate, and form a localized infection. Because the host's immunity is relatively high or the organism's virulence is low, the body walls off the infection rather than allowing it to spread. **Analysis of Incorrect Options:** * **Epiphysis:** Rarely the primary site. Infection usually only involves the epiphysis if it crosses the growth plate (more common in infants) or occurs after the growth plate has fused. * **Diaphysis:** While osteomyelitis can involve the shaft, it is less common for a localized Brodie’s abscess to originate here due to the lack of the specific capillary loops found in the metaphysis. * **Epiphyseal cartilage:** This acts as a mechanical barrier to the spread of infection in children; it is not a site for abscess formation. **Clinical Pearls for NEET-PG:** * **Most Common Organism:** *Staphylococcus aureus*. * **Most Common Site:** Proximal tibia (followed by distal femur). * **Classic X-ray Finding:** A well-defined radiolucent (lytic) lesion surrounded by a rim of **sclerotic bone**. * **Clinical Presentation:** Chronic limb pain, often worse at night, relieved by aspirin (mimicking Osteoid Osteoma). * **Treatment:** Surgical curettage and evacuation under antibiotic cover.

Question 118: What is the most common cause of bony ankylosis?

A. Tuberculosis of the hip
B. Tuberculosis of the knee
C. Septic arthritis (Correct Answer)
D. Pott's spine

Explanation: ### Explanation **Correct Option: C. Septic Arthritis** The hallmark of **Septic Arthritis** (pyogenic arthritis) is the rapid destruction of articular cartilage. Pyogenic organisms (like *Staphylococcus aureus*) produce proteolytic enzymes and trigger a massive release of lysosomal enzymes from polymorphonuclear leukocytes. This leads to the complete loss of the joint space and the exposure of subchondral bone. When the two denuded bony surfaces heal together, they form a solid bridge of bone, resulting in **Bony Ankylosis**. **Analysis of Incorrect Options:** * **A & B. Tuberculosis (Hip/Knee):** In skeletal tuberculosis, the infection is chronic and characterized by the formation of "pannus" (granulation tissue). This tissue typically destroys the periphery of the joint first, often sparing the central cartilage for a long time. Healing in TB usually occurs via fibrosis, leading to **Fibrous Ankylosis**, not bony. * **D. Pott’s Spine:** While spinal TB can lead to bony fusion of the vertebral bodies (syndesmophytes or block vertebrae) during the healing phase, it is not the "most common" cause of bony ankylosis when compared to the systemic incidence and rapid destructive nature of pyogenic septic arthritis in peripheral joints. **High-Yield Clinical Pearls for NEET-PG:** * **Bony Ankylosis:** Most common in **Septic Arthritis** and **Ankylosing Spondylitis**. * **Fibrous Ankylosis:** Most common in **Tuberculosis** and **Rheumatoid Arthritis**. * **Exception to the Rule:** Tuberculosis of the **spine (Pott's spine)** is a notable exception where bony ankylosis is more common than in peripheral TB joints. * **Radiology Tip:** On X-ray, bony ankylosis is identified by the presence of trabecular bone crossing the joint space, whereas fibrous ankylosis shows a blurred joint space without bony bridges.

Question 119: Ely's cysts are a feature of which of the following conditions?

A. Osteoarthritis of temporomandibular joint (Correct Answer)
B. Chronic suppurative osteomyelitis
C. Fibrous dysplasia
D. Gorlin-Goltz syndrome

Explanation: **Explanation:** **Ely’s cysts** (also known as subchondral cysts) are a classic radiological hallmark of **Osteoarthritis (OA)**, particularly when it affects the **temporomandibular joint (TMJ)**. These are well-defined, radiolucent areas located just beneath the articular surface of the mandibular condyle. They occur when synovial fluid is forced into the subchondral bone through microfractures in the degenerated articular cartilage, leading to localized bone resorption. **Analysis of Options:** * **Option A (Correct):** In TMJ Osteoarthritis, the loss of joint space, osteophyte formation (lipping), and subchondral sclerosis are accompanied by Ely’s cysts. * **Option B (Incorrect):** Chronic suppurative osteomyelitis is characterized by **sequestrum** (dead bone), **involucrum** (new bone sheath), and cloacae, rather than subchondral cysts. * **Option C (Incorrect):** Fibrous dysplasia typically presents with a characteristic **"ground-glass"** appearance due to the replacement of normal bone with fibrous tissue. * **Option D (Incorrect):** Gorlin-Goltz syndrome (Nevoid Basal Cell Carcinoma Syndrome) is associated with multiple **Odontogenic Keratocysts (OKCs)** in the jaw, not Ely's cysts. **High-Yield Clinical Pearls for NEET-PG:** * **Radiological Triad of OA:** Joint space narrowing, subchondral sclerosis, and osteophytes. * **Ely’s Cysts vs. Geodes:** While "Ely’s cyst" is the specific eponym used in TMJ/dental literature, these are pathologically identical to **Geodes** seen in OA of the hip or knee and in Rheumatoid Arthritis. * **TMJ OA:** Often presents with "crepitus" on jaw movement and a "dull ache" exacerbated by chewing.

Question 120: A young child is diagnosed with chronic osteomyelitis of the tibia and has started on sensitive antibiotics. Which of the following parameters is best to monitor the response to antibiotic therapy after 6 days?

A. Erythrocyte Sedimentation Rate (ESR)
B. C-reactive protein (CRP) (Correct Answer)
C. Differential White Blood Cell (WBC) count
D. Total White Blood Cell (WBC) count

Explanation: **Explanation:** In the management of musculoskeletal infections like osteomyelitis, monitoring the response to therapy is crucial. **C-reactive protein (CRP)** is the most sensitive and reliable marker for this purpose. **1. Why CRP is the Correct Answer:** CRP is an acute-phase reactant with a very short half-life (approximately 19 hours). Its levels rise rapidly (within 6 hours) in response to inflammation and, more importantly, **fall rapidly** once the infection is controlled by effective antibiotics. By day 6 of treatment, a declining CRP level is the most accurate biochemical indicator that the chosen antibiotic is effective. **2. Why Other Options are Incorrect:** * **Erythrocyte Sedimentation Rate (ESR):** While ESR is a good screening tool, it has a slow response time. It takes days to peak and weeks to return to normal (slow lag phase). Therefore, at 6 days, it may still be elevated despite clinical improvement, making it a poor tool for acute monitoring. * **Total and Differential WBC Count:** These are often the first to normalize, sometimes even before the infection is fully under control. They lack the specificity and sensitivity of CRP for monitoring the ongoing inflammatory process in bone. **Clinical Pearls for NEET-PG:** * **CRP vs. ESR:** CRP is the first to rise and the first to fall. ESR is the last to fall. * **Diagnosis vs. Monitoring:** While both ESR and CRP are used for diagnosis, **CRP is the "Gold Standard" for monitoring** treatment response in pediatric osteomyelitis and septic arthritis. * **Prognostic Value:** If CRP does not begin to drop within 48–72 hours of starting antibiotics, it suggests treatment failure, a resistant organism, or the need for surgical drainage.

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

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free