Arthrology and Infections — MCQs

Arthrology and Infections Indian Medical PG Practice Questions and MCQs

Question 71: Which of the following causes bony ankylosis?

A. Tuberculosis
B. Septic arthritis (Correct Answer)
C. Gouty arthritis
D. Behçet's disease

Explanation: ### Explanation **Correct Option: B. Septic Arthritis** The hallmark of **Septic Arthritis** (pyogenic arthritis) is the rapid destruction of articular cartilage. Proteolytic enzymes (lysosomal enzymes) released by polymorphonuclear leukocytes (neutrophils) and the infecting bacteria (e.g., *Staphylococcus aureus*) digest the proteoglycans and collagen of the cartilage. Once the protective hyaline cartilage is destroyed, the underlying raw bony surfaces come into contact and fuse, leading to **Bony Ankylosis**. **Analysis of Incorrect Options:** * **A. Tuberculosis (TB) Arthritis:** TB typically causes **Fibrous Ankylosis**. The *Mycobacterium tuberculosis* lacks the potent proteolytic enzymes found in pyogenic bacteria. Instead, it causes a slow destruction of cartilage via "pannus" formation, resulting in a joint bridged by fibrous tissue rather than bone. (Exception: TB of the spine/Pott’s spine often leads to bony fusion). * **C. Gouty Arthritis:** This is a metabolic arthropathy caused by urate crystal deposition. While it leads to joint destruction (punched-out erosions), it typically results in joint deformity or secondary osteoarthritis rather than bony ankylosis. * **D. Behçet’s Disease:** This is a multi-system inflammatory disorder characterized by recurrent oral and genital ulcers. The associated arthritis is usually non-erosive and self-limiting, rarely leading to permanent joint fusion. **High-Yield Clinical Pearls for NEET-PG:** * **Bony Ankylosis** is most commonly seen in: **Septic Arthritis** and **Ankylosing Spondylitis**. * **Fibrous Ankylosis** is most commonly seen in: **Tuberculosis** and **Rheumatoid Arthritis**. * **Triple Deformity of the Knee** (flexion, posterior subluxation, and external rotation) is a classic sequela of neglected TB of the knee. * The earliest radiological sign of Septic Arthritis is **joint space widening** (due to effusion), followed by rapid joint space narrowing.

Question 72: Melon seed bodies are found in which of the following conditions?

A. Chondrocalcinosis
B. Gout
C. Tuberculous tenosynovitis (Correct Answer)
D. Osteoarthritis of the wrist

Explanation: **Explanation:** **Melon seed bodies** are characteristic macroscopic findings most commonly associated with **Tuberculous (TB) tenosynovitis**, particularly involving the flexor tendons of the wrist (Compound Palmar Bursa). 1. **Why Tuberculous Tenosynovitis is correct:** These bodies are formed due to chronic inflammation of the synovial lining. Fibrin deposits result from the exudative phase of tuberculosis; as the joint or tendon sheath moves, these fibrin masses are compressed and molded into small, smooth, white, oval structures resembling melon or rice seeds. They are typically found floating within the synovial fluid or attached to the synovium. 2. **Why other options are incorrect:** * **Chondrocalcinosis (Pseudogout):** Characterized by the deposition of **Calcium Pyrophosphate Dihydrate (CPPD)** crystals in cartilage, appearing as linear calcifications on X-ray, not fibrin bodies. * **Gout:** Involves the deposition of **Monosodium Urate** crystals. While it causes "tophi," these are chalky-white gritty deposits, not smooth melon seed bodies. * **Osteoarthritis:** A degenerative joint disease characterized by joint space narrowing, osteophytes, and subchondral sclerosis, rather than proliferative synovial fibrin bodies. **High-Yield Clinical Pearls for NEET-PG:** * **Compound Palmar Bursa:** TB tenosynovitis often presents as a "dumbbell-shaped" swelling across the flexor retinaculum (Cross-fluctuation sign). * **Rice Bodies:** While "Melon seed bodies" is the classic term for TB, similar "Rice bodies" can occasionally be seen in **Rheumatoid Arthritis (RA)** due to chronic synovial inflammation. * **Microscopy:** In TB, look for Caseating granulomas; in Gout, look for Needle-shaped negatively birefringent crystals.

Question 73: Triple deformity of the knee is classically seen in which of the following conditions?

A. Tuberculosis
B. Rheumatic arthritis
C. Fracture patella
D. Rheumatoid arthritis (Correct Answer)

Explanation: **Explanation:** The **Triple Deformity of the Knee** is a classic late-stage manifestation of **Rheumatoid Arthritis (RA)**. It occurs due to chronic synovitis, which leads to the destruction of articular cartilage and laxity of the stabilizing ligaments (specifically the ACL and PCL). The deformity consists of three distinct components: 1. **Flexion:** Caused by the dominant action of the hamstrings. 2. **Posterior Subluxation of the Tibia:** Due to the loss of cruciate ligament integrity. 3. **External Rotation of the Tibia:** Caused by the pull of the Biceps Femoris muscle. **Analysis of Options:** * **Rheumatoid Arthritis (Correct):** The systemic inflammatory nature of RA leads to pannus formation, ligamentous laxity, and muscle imbalances that pull the joint into this characteristic position. * **Tuberculosis (TB) of the Knee:** While TB can cause a "triple deformity" in advanced stages (Stage of Destruction), it is more classically associated with **"Night Starts"** and **"Fleeting Pains."** In modern exams, RA remains the primary association for this specific terminology. * **Rheumatic Arthritis:** This typically presents as a migratory polyarthritis that involves large joints but resolves without causing permanent structural deformities or subluxations. * **Fracture Patella:** This is a traumatic injury leading to loss of the extensor mechanism, not a progressive multi-planar deformity. **High-Yield Clinical Pearls for NEET-PG:** * **Baker’s Cyst:** Often associated with RA of the knee due to synovial herniation. * **Genu Valgum:** The most common coronal plane deformity in RA (whereas Genu Varum is more common in Osteoarthritis). * **Treatment:** In the stage of triple deformity, the treatment of choice is usually **Total Knee Arthroplasty (TKA)**.

Question 74: What condition is associated with a 'frozen pelvis'?

A. Osteoarthritis
B. Pott's disease (Correct Answer)
C. Actinomycosis
D. Reiter's disease

Explanation: ### Explanation **Pott’s Disease (Tuberculosis of the Spine)** is the correct answer. The term **'frozen pelvis'** in an orthopaedic context refers to a complication of advanced spinal tuberculosis involving the lower lumbar vertebrae or the lumbosacral junction. When the tubercular infection spreads, it often leads to the formation of a **cold abscess**. This abscess can track down the psoas muscle sheath (Psoas abscess) and infiltrate the pelvic fascia and cellular tissue. Chronic inflammation and subsequent extensive fibrosis cause the pelvic organs and structures to become densely adherent and fixed. This rigid, immobile state of the pelvic contents is clinically described as a 'frozen pelvis.' #### Analysis of Incorrect Options: * **A. Osteoarthritis:** This is a degenerative joint disease characterized by cartilage loss and osteophyte formation. While it causes joint stiffness (e.g., in the hip), it does not cause the extensive soft-tissue fibrosis or "freezing" of the pelvic cavity. * **C. Actinomycosis:** While this granulomatous infection can cause "woody" induration and multiple discharging sinuses (often in the cervicofacial or abdominal regions), it is not the classic association for 'frozen pelvis' in standard orthopaedic teaching compared to TB. * **D. Reiter’s Disease (Reactive Arthritis):** This presents with the triad of urethritis, conjunctivitis, and arthritis. It typically affects the sacroiliac joints and large joints of the lower limb but does not lead to pelvic fibrosis. #### NEET-PG High-Yield Pearls: * **Pott’s Paraplegia:** The most common complication of spinal TB. * **Cold Abscess:** Named so because it lacks the traditional signs of inflammation (heat, redness). * **Psoas Sign:** Pain on hip extension, often seen when a Pott's abscess involves the psoas muscle. * **Radiology:** The earliest sign of Pott's disease on X-ray is the narrowing of the intervertebral disc space and blurring of the vertebral endplates.

Question 75: Osteomyelitis in sickle cell anemia is most commonly due to which organism?

A. Salmonella (Correct Answer)
B. Streptococcus
C. Hemophilus
D. Neisseria

Explanation: **Explanation:** In the general population, **Staphylococcus aureus** is the most common cause of osteomyelitis. However, in patients with **Sickle Cell Anemia (SCA)**, **Salmonella** species are the most frequently isolated pathogens. **Why Salmonella?** The predisposition to Salmonella in SCA is due to several factors: 1. **Hyposplenism:** Functional asplenia from repeated splenic infarcts reduces the clearance of encapsulated organisms. 2. **Intestinal Infarcts:** Vaso-occlusive crises cause micro-infarcts in the gut mucosa, allowing Salmonella (normal flora in some) to enter the bloodstream. 3. **Expanded Bone Marrow:** Chronic hemolysis leads to marrow hyperplasia and sluggish blood flow, creating a nidus for infection. 4. **Impaired Macrophage Function:** The reticuloendothelial system is "overloaded" with RBC breakdown products, compromising the killing of Salmonella. **Analysis of Incorrect Options:** * **B. Streptococcus:** While *S. pneumoniae* is a common cause of sepsis in SCA due to asplenia, it is not the primary cause of osteomyelitis. * **C. Hemophilus:** *H. influenzae* was a common cause of osteomyelitis in young children historically, but its incidence has significantly decreased due to the HiB vaccine. * **D. Neisseria:** This organism is associated with septic arthritis (specifically *N. gonorrhoeae* in sexually active adults) rather than osteomyelitis. **Clinical Pearls for NEET-PG:** * **Most common overall:** If the question asks for the most common cause of osteomyelitis in SCA and both are listed, **Salmonella** is the classic "textbook" answer. However, some recent studies suggest *S. aureus* is becoming equally prevalent; always prioritize Salmonella for exams unless specified otherwise. * **Radiology:** The earliest sign of osteomyelitis on X-ray is **soft tissue swelling** (takes 10–14 days for bone changes). * **Investigation of Choice:** **MRI** is the most sensitive imaging modality for early diagnosis.

Question 76: What is the commonest site of skeletal tuberculosis?

A. Tibia
B. Radius
C. Humerus
D. Vertebrae (Correct Answer)

Explanation: **Explanation:** **Skeletal Tuberculosis (TB)** accounts for approximately 1–3% of all TB cases and about 10–15% of extrapulmonary TB cases. **Why Vertebrae is the correct answer:** The **spine (Vertebrae)** is the most common site of skeletal tuberculosis, accounting for approximately **50% of all cases**. This condition is known as **Pott’s Disease**. The infection typically involves the anterior part of the vertebral body and spreads under the anterior longitudinal ligament to involve adjacent levels. The high incidence in the spine is attributed to the rich vascular supply (Batson’s venous plexus) which facilitates the hematogenous spread of *Mycobacterium tuberculosis* from a primary focus (usually lungs or lymph nodes). Within the spine, the **Dorsolumbar (Thoracolumbar) junction** is the most frequently affected region. **Why other options are incorrect:** * **Tibia, Radius, and Humerus:** While TB can affect long bones (osteomyelitis) or joints (hip and knee being the most common after the spine), these sites are significantly less common than spinal involvement. Long bone TB usually presents as a cystic lesion or focal osteomyelitis, but it does not match the epidemiological prevalence of Pott’s disease. **High-Yield Clinical Pearls for NEET-PG:** * **Most common joint affected:** Hip joint (followed by the Knee). * **Paradiscal type:** The most common pattern of spinal TB (affects the disc space and adjacent vertebrae). * **Cold Abscess:** A hallmark of skeletal TB, characterized by a collection of pus/debris without traditional signs of inflammation (heat or redness). * **Psoas Abscess:** Often associated with lumbar TB, tracking down the psoas muscle sheath. * **Gibbus Deformity:** A sharp kyphotic angulation resulting from the collapse of anterior vertebral bodies.

Question 77: What is the investigation of choice for spinal tuberculosis?

A. X-ray
B. CT Scan
C. MRI (Correct Answer)
D. PET Scan

Explanation: **Explanation:** **Spinal Tuberculosis (Pott’s Disease)** is the most common site of skeletal tuberculosis. **MRI (Magnetic Resonance Imaging)** is the investigation of choice because it provides superior soft-tissue contrast, allowing for the earliest detection of the disease—often weeks before changes appear on a plain X-ray. **Why MRI is the Correct Answer:** * **Early Detection:** It can identify marrow edema and early inflammatory changes in the vertebral bodies. * **Soft Tissue Detail:** It is the gold standard for visualizing **pre-vertebral, para-vertebral, and psoas abscesses**. * **Neural Assessment:** It accurately assesses the extent of spinal cord compression, the presence of granulation tissue, and the "bird’s nest" appearance of debris, which is crucial for prognosticating neurological deficits. **Why Other Options are Incorrect:** * **X-ray:** It is the initial screening tool but lacks sensitivity. Bony destruction is only visible on X-ray after **30-50% of bone mineral density** is lost. * **CT Scan:** While excellent for visualizing bony anatomy, sequestra (dead bone), and calcification within abscesses, it is inferior to MRI in evaluating the spinal cord and early marrow changes. * **PET Scan:** Useful for identifying multi-focal systemic involvement or monitoring metabolic response to treatment, but it is not the primary diagnostic modality for spinal TB. **High-Yield Clinical Pearls for NEET-PG:** * **Earliest sign on X-ray:** Rarefaction of the vertebral endplates and narrowing of the disc space. * **Paradiscal type:** The most common pattern of involvement (affects adjacent vertebrae and the intervening disc). * **Cold Abscess:** Characterized by a lack of traditional signs of inflammation (heat/redness). * **Gibbus Deformity:** A sharp kyphotic angulation resulting from the collapse of anterior vertebral bodies.

Question 78: What is the most common cause of chronic osteomyelitis?

A. Staphylococcus aureus (Correct Answer)
B. Streptococcus pyogenes
C. Mycobacterium tuberculosis
D. Staphylococcus epidermidis

Explanation: **Explanation:** **Staphylococcus aureus** is the most common causative organism for both acute and chronic hematogenous osteomyelitis across almost all age groups. Its dominance is attributed to specific virulence factors, such as **surface adhesins** (which allow it to bind to bone matrix components like collagen) and the ability to form **biofilms**. In chronic cases, the bacteria can survive within the **sequestrum** (dead bone) and inside osteoblasts, making them resistant to both host immune responses and systemic antibiotics. **Analysis of Incorrect Options:** * **Streptococcus pyogenes:** While a common cause of skin and soft tissue infections (cellulitis), it is a much less frequent cause of bone infections compared to Staph. aureus. * **Mycobacterium tuberculosis:** This is the most common cause of **granulomatous** osteomyelitis (e.g., Pott’s spine). While chronic in nature, it is not the most common cause of general chronic pyogenic osteomyelitis. * **Staphylococcus epidermidis:** This is a coagulase-negative staphylococcus (CoNS) and is the most common cause of infections associated with **prosthetic implants** or indwelling devices, but not the primary cause of native chronic osteomyelitis. **High-Yield Clinical Pearls for NEET-PG:** * **Sickle Cell Disease:** *Salmonella* is a high-yield association, though *Staph. aureus* remains a frequent co-contender. * **IV Drug Users:** Increased incidence of *Pseudomonas aeruginosa* (often affecting the spine or sacroiliac joints). * **Neonates:** *Group B Streptococcus* and *E. coli* are significant pathogens alongside *Staph. aureus*. * **Pathognomonic Sign:** The presence of a **sequestrum** (dead bone) and **involucrum** (new bone sheath) on X-ray is the hallmark of chronic osteomyelitis.

Question 79: What is the recommended total duration of antibiotic therapy for acute osteomyelitis?

A. 4 weeks
B. 2 weeks
C. 6 weeks (Correct Answer)
D. 8 weeks

Explanation: **Explanation:** The management of **acute osteomyelitis** requires a prolonged course of antibiotics because bone is a relatively avascular tissue with poor penetration of antimicrobial agents. The goal is to achieve complete eradication of the pathogen to prevent the infection from transitioning into chronic osteomyelitis. **1. Why 6 weeks is correct:** The standard recommendation for acute osteomyelitis is a total duration of **4 to 6 weeks**. In the context of NEET-PG and standard orthopedic textbooks (like Campbell’s or Apley’s), **6 weeks** is the preferred answer. This duration ensures that the infection is cleared from the haversian systems and prevents recurrence. Usually, the treatment begins with 1–2 weeks of intravenous (IV) antibiotics, followed by oral therapy once clinical improvement and a decline in inflammatory markers (CRP/ESR) are observed. **2. Why other options are incorrect:** * **2 weeks (B):** This is insufficient for bone infections. While symptoms may subside, the bacteria often persist within the bone matrix, leading to a high risk of relapse. * **4 weeks (A):** While 4 weeks is the minimum threshold for some uncomplicated pediatric cases, 6 weeks remains the gold standard for ensuring complete resolution in a general clinical context. * **8 weeks (D):** This duration is typically reserved for chronic osteomyelitis or infections involving resistant organisms (like MRSA) and prosthetic joints, rather than uncomplicated acute osteomyelitis. **High-Yield Clinical Pearls for NEET-PG:** * **Most common organism:** *Staphylococcus aureus* (overall). * **Most common organism in Sickle Cell Anemia:** *Salmonella*. * **Earliest X-ray sign:** Soft tissue swelling (appears in 3–5 days); bone changes (periosteal reaction/rarefaction) take 10–14 days to appear. * **Investigation of choice:** **MRI** (most sensitive and specific for early diagnosis). * **Gold Standard for diagnosis:** Bone biopsy and culture.

Question 80: Wandering acetabulum is seen in which of the following conditions?

A. Tuberculosis (Correct Answer)
B. Gout
C. Rheumatoid arthritis
D. Ankylosing spondylitis

Explanation: **Explanation:** **Wandering Acetabulum** (also known as *Pestle and Mortar* appearance) is a classic radiological feature of **Tuberculosis (TB) of the hip**. In TB hip, chronic granulomatous inflammation leads to the destruction of the superior-posterior margin of the acetabulum. Due to the constant upward pressure from the femoral head and the weakening of the bone, the femoral head gradually migrates superiorly and laterally. This creates a "pseudo-acetabulum" above the original one, giving the appearance that the acetabulum has "wandered" upwards. **Analysis of Options:** * **Tuberculosis (Correct):** Characterized by the triad of joint space narrowing, peripheral osseous erosions, and profound juxta-articular osteopenia (Phemister’s triad). The destruction of the acetabular roof leads to the wandering acetabulum. * **Gout:** Typically involves small joints (first MTP joint). Radiologically, it shows "punched-out" erosions with overhanging edges (Martel’s sign), not proximal migration of the hip. * **Rheumatoid Arthritis:** Causes uniform joint space narrowing and axial protrusion of the acetabulum (*Protrusio Acetabuli*), where the femoral head moves medially, rather than superiorly. * **Ankylosing Spondylitis:** Primarily affects the sacroiliac joints and spine. In the hip, it leads to joint space narrowing and eventual bony ankylosis (fusion), not a wandering acetabulum. **Clinical Pearls for NEET-PG:** * **Protrusio Acetabuli (Otto’s Pelvis):** Seen in Rheumatoid Arthritis, Paget’s disease, and Osteomalacia. * **Phemister’s Triad:** Diagnostic of Joint TB (Juxta-articular osteopenia, peripheral erosions, and late preservation of joint space). * **Bird’s Flight Appearance:** Seen on X-ray in the late stages of TB hip.

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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