Arthrology and Infections Practice Questions

Q: All of the following are properties of synovial fluid except:

Normal WBC count in synovial fluid is 350–3500/mm³.. **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.

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

Malignancy. **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).

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

1st week. 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.

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

Thoracic. **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).

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

Metaphysis. **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.

Q: What is the most common cause of bony ankylosis?

Septic arthritis. ### 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.

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

Osteoarthritis of temporomandibular joint. **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.

Q: 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?

C-reactive protein (CRP). **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.

Question 1

What is the treatment of triple deformity?

Accepted Answer

Anti-tetanus therapy (ATT), immobilization, and debridement

Answer

Anti-tetanus therapy (ATT)

Answer

Anti-tetanus therapy (ATT) plus immobilization

Answer

None of the above

Question 2

All of the following are properties of synovial fluid except:

Accepted Answer

Normal WBC count in synovial fluid is 350–3500/mm³.

Answer

It is a pale yellow, clear, and sufficiently viscous fluid that droplets expelled from a needle tip fall in a long string.

Answer

It is a Non-Newtonian fluid.

Answer

It doesn't clot since it lacks fibrinogen.

Question 3

Which of the following is NOT a complication of acute osteomyelitis?

Accepted Answer

Malignancy

Answer

Fracture of the affected bone

Answer

Sepsis

Answer

Chronicity

Question 4

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

Accepted Answer

1st week

Answer

Less than 2 weeks

Answer

2nd week

Answer

3rd week

Question 5

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

Accepted Answer

Thoracic

Answer

Cervical

Answer

Lumbar

Answer

Sacral

Question 6

Suppurative osteomyelitis is primarily caused by which pathogen?

Accepted Answer

Streptococci initially, with subsequent replacement by staphylococci

Answer

Staphylococci

Answer

Streptococci

Answer

Staphylococci initially, with subsequent replacement by streptococci

Question 7

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

Accepted Answer

Metaphysis

Answer

Epiphysis

Answer

Diaphysis

Answer

Epiphyseal cartilage

Question 8

What is the most common cause of bony ankylosis?

Accepted Answer

Septic arthritis

Answer

Tuberculosis of the hip

Answer

Tuberculosis of the knee

Answer

Pott's spine

Question 9

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

Accepted Answer

Osteoarthritis of temporomandibular joint

Answer

Chronic suppurative osteomyelitis

Answer

Fibrous dysplasia

Answer

Gorlin-Goltz syndrome

Question 10

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?

Accepted Answer

C-reactive protein (CRP)

Answer

Erythrocyte Sedimentation Rate (ESR)

Answer

Differential White Blood Cell (WBC) count

Answer

Total White Blood Cell (WBC) count

Arthrology and Infections — MCQs

Arthrology and Infections — MCQs

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