Arthrology and Infections — MCQs

Q: Osteosclerosis of bone occurs due to?

Increased host response. ### Explanation **Concept Overview:** Osteosclerosis refers to an abnormal increase in bone density, characterized by thickening of the trabeculae and narrowing of the medullary canal. In the context of infections (like chronic osteomyelitis), it represents a **productive or formative bone response** rather than a destructive one. **Why Option C is Correct:** Osteosclerosis occurs when the **host’s immune response is strong** and the infecting organism’s virulence is relatively low. This balance allows the body to contain the infection by stimulating osteoblastic activity, leading to the formation of dense, sclerotic bone. A classic clinical example is **Garré’s Sclerosing Osteomyelitis**, where the body reacts to a low-grade chronic infection by producing massive subperiosteal new bone and sclerosis without significant suppuration or sequestration. **Why Other Options are Incorrect:** * **Options A & D:** Decreased host resistance or an immunocompromised state typically leads to rapid, aggressive bone destruction (osteolysis) and systemic spread, rather than the organized, dense bone formation seen in sclerosis. * **Option B:** High virulence of an organism usually results in acute suppuration, abscess formation, and bone necrosis (sequestrum). Sclerosis is a hallmark of a chronic, low-grade process where the host is "winning" the battle or maintaining a stalemate. **High-Yield Clinical Pearls for NEET-PG:** * **Garré’s Sclerosing Osteomyelitis:** Most common in the mandible and tibia; characterized by "onion-skin" periosteal reaction and dense sclerosis. * **Brodie’s Abscess:** Another form of high host resistance where a subacute infection is localized and walled off by a rim of sclerotic bone. * **Radiological Sign:** On X-ray, osteosclerosis appears as increased radiopacity (whiteness) and loss of the normal trabecular pattern.

Q: What is the usual site of tuberculous bursitis?

Trochanteric. ### Explanation **Correct Option: D. Trochanteric** Tuberculous bursitis is a chronic granulomatous inflammation caused by *Mycobacterium tuberculosis*. Among all the bursae in the human body, the **Trochanteric bursa** (located between the greater trochanter and the gluteus maximus/tensor fasciae latae) is the **most common site** of involvement. The pathogenesis usually involves the hematogenous spread of the bacilli or direct extension from an underlying focus of osteomyelitis in the greater trochanter. Clinically, it presents as a "cold abscess" over the lateral aspect of the hip, often associated with a limp and local tenderness, though hip joint movements usually remain preserved in the early stages. **Why other options are incorrect:** * **A. Prepatellar:** While the prepatellar bursa is a common site for *septic* (pyogenic) or *traumatic* bursitis (Housemaid’s knee), it is rarely affected by tuberculosis. * **B & C. Subacromial and Subdeltoid:** These bursae are occasionally involved in TB, often secondary to tuberculosis of the shoulder joint (Caries Sicca), but they are statistically less common than trochanteric involvement. **Clinical Pearls for NEET-PG:** * **Pathognomonic Sign:** The presence of **"Rice bodies"** (fibrin masses) within the bursal fluid is a classic finding in tuberculous bursitis and rheumatoid arthritis. * **Radiology:** X-rays may show soft tissue swelling and irregular erosions of the greater trochanter (the "hidden" primary focus). * **Treatment:** Management involves a combination of Anti-Tubercular Therapy (ATT) and surgical excision (bursectomy) if the disease is extensive or recalcitrant. * **Differential Diagnosis:** Must be distinguished from "Snapping Hip Syndrome" and Trochanteric Pain Syndrome.

Q: A 45-year-old patient presents with symptoms of septic arthritis. What is the most common cause in this patient?

Staphylococcus aureus. **Explanation:** Septic arthritis is a medical emergency characterized by the infection of a joint space. In adults, the most common route of infection is **hematogenous spread**. **1. Why Staphylococcus aureus is correct:** *Staphylococcus aureus* is the **most common overall cause** of septic arthritis across all age groups (except neonates, where Group B Streptococcus is significant). It is a highly virulent organism that produces proteases, which can lead to rapid joint destruction if not treated promptly. In a 45-year-old patient, unless specific risk factors (like IV drug use or STIs) are mentioned, *S. aureus* remains the statistical primary pathogen. **2. Analysis of Incorrect Options:** * **A. Gonococcus:** *Neisseria gonorrhoeae* is a common cause of septic arthritis in **young, sexually active adults**. It often presents with a triad of tenosynovitis, dermatitis, and polyarthralgia. However, *S. aureus* still holds a higher overall prevalence in the general adult population. * **C. Salmonella:** This is a high-yield association for patients with **Sickle Cell Anemia**. While *S. aureus* is still common in these patients, *Salmonella* is a characteristic and frequently tested pathogen for this specific demographic. * **D. Pneumococci:** *Streptococcus pneumoniae* can cause septic arthritis but is much less common than Staphylococci, usually occurring secondary to pneumonia or meningitis. **High-Yield Clinical Pearls for NEET-PG:** * **Most common joint involved:** Knee joint (>50% of cases). * **Gold Standard Diagnosis:** Arthrocentesis (Joint fluid analysis) showing WBC count >50,000/mm³ with >75% polymorphonuclear cells. * **IV Drug Users:** Increased incidence of infection in fibrocartilaginous joints (Sternoclavicular and Sacroiliac joints); common organisms include *Pseudomonas aeruginosa*. * **Prosthetic Joints:** *Staphylococcus epidermidis* is a frequent culprit.

Q: All of the following statements about synovial fluid are true, except-

Secreted primarily by type A synovial cells. ### Explanation **Concept Overview:** Synovial fluid is a ultrafiltrate of blood plasma supplemented with high concentrations of hyaluronic acid. It is produced by the **synovium**, which consists of two distinct types of synoviocytes: **Type A** (macrophage-like) and **Type B** (fibroblast-like) cells. **Why Option B is the Correct Answer (The False Statement):** The primary function of **Type A synoviocytes** is phagocytosis (clearing debris from the joint space). It is the **Type B synoviocytes** that are responsible for the synthesis and secretion of hyaluronic acid and lubricin, which give synovial fluid its unique properties. Therefore, stating that it is secreted primarily by Type A cells is incorrect. **Analysis of Other Options:** * **Option A (Non-Newtonian kinetics):** This is **true**. Synovial fluid does not have a constant viscosity; its flow properties change under pressure. * **Option C (Contains Hyaluronic acid):** This is **true**. Hyaluronic acid is the key component that provides high viscosity and lubrication to the joint. * **Option D (Viscosity is variable):** This is **true**. Due to its non-Newtonian nature (specifically "thixotropic" behavior), the viscosity decreases as the shear rate increases (e.g., during rapid joint movement). **High-Yield Clinical Pearls for NEET-PG:** * **Normal Synovial Fluid:** Clear, straw-colored, high viscosity, and contains <200 WBCs/mm³. * **String Sign:** A test for viscosity; normal fluid forms a 3–5 cm "string" when dropped from a syringe. Viscosity is **decreased** in inflammatory conditions like Rheumatoid Arthritis. * **Mucin Clot Test:** Adding acetic acid to normal synovial fluid forms a tight clot (due to hyaluronic acid). A poor/friable clot indicates inflammation or infection. * **Septic Arthritis:** Characterized by a WBC count typically >50,000/mm³ and low glucose levels.

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

Pyogenic arthritis. **Explanation:** **Bony ankylosis** refers to the complete fusion of a joint due to the proliferation of bone across the joint space, resulting in total loss of movement. **Why Pyogenic Arthritis is the Correct Answer:** Pyogenic (septic) arthritis is the most common cause of bony ankylosis. The underlying mechanism involves the release of proteolytic enzymes by polymorphonuclear leukocytes (neutrophils) and bacteria. These enzymes rapidly destroy the articular cartilage, exposing the subchondral bone. During the healing phase, the intense inflammatory response leads to the formation of a bridge of new bone (callus) across the joint, resulting in permanent osseous fusion. **Analysis of Incorrect Options:** * **Rheumatoid Arthritis (RA):** RA typically leads to **fibrous ankylosis**. While bony fusion can occur (especially in the carpal and tarsal bones), the primary pathology is a chronic proliferative synovitis (pannus) that erodes cartilage but rarely results in complete bony bridge formation compared to pyogenic infections. * **Traumatic Arthritis:** This usually leads to secondary osteoarthritis. While severe intra-articular fractures can lead to fusion, it is statistically less common than infection-induced ankylosis. * **Osteoarthritis (OA):** OA is characterized by the loss of joint space and osteophyte formation, but it **never** results in ankylosis. The joint remains mobile, albeit painful and restricted. **NEET-PG High-Yield Pearls:** * **Pyogenic Arthritis:** Leads to **Bony** ankylosis. * **Tuberculous (TB) Arthritis:** Classically leads to **Fibrous** ankylosis (except in the spine/Pott’s disease, where bony fusion is common). * **Ankylosing Spondylitis:** A classic cause of bony ankylosis of the **axial skeleton** (SI joints and spine). * **Most common organism in Pyogenic Arthritis:** *Staphylococcus aureus* (overall); *Neisseria gonorrhoeae* (sexually active young adults).

Q: On X-ray, dead bone appears as:

More radiopaque. **Explanation:** The correct answer is **B. More radiopaque**. In the context of bone pathology, specifically **Chronic Osteomyelitis**, dead bone is referred to as a **Sequestrum**. It appears more radiopaque (whiter/denser) on an X-ray due to three primary reasons: 1. **Loss of Blood Supply:** Dead bone has no blood flow, preventing the action of osteoclasts. Therefore, it cannot undergo bone resorption. 2. **Relative Sclerosis:** Surrounding living bone undergoes "disuse osteoporosis" (hyperemic decalcification) due to inflammation and lack of use, making the dead bone look denser by comparison. 3. **Physical Changes:** The sequestrum may undergo some physical compression and mineral precipitation, further increasing its density. **Analysis of Incorrect Options:** * **A. More radiolucent:** This indicates bone loss or decreased mineral density, seen in acute infections, tumors, or metabolic bone diseases (osteoporosis). * **C. With osteophytes:** These are bony projections associated with **Osteoarthritis** (degenerative joint disease), not bone death. * **D. Soap-bubble appearance:** This is a classic radiological sign of **Giant Cell Tumor (GCT)** of the bone or occasionally Adamantinoma, characterized by expansive, multiloculated lucent lesions. **NEET-PG High-Yield Pearls:** * **Sequestrum:** Dead bone (Radiopaque). * **Involucrum:** A layer of new living bone formed around the sequestrum (derived from the periosteum). * **Cloaca:** An opening in the involucrum through which pus and sequestra are discharged. * **Brodie’s Abscess:** A form of subacute/chronic osteomyelitis appearing as a radiolucent nidus surrounded by sclerosis, typically in the metaphysis.

Q: A 60-year-old person suffering from myositis ossificans progressiva has which of the following as the usual cause of death?

Lung disease. **Explanation:** **Myositis Ossificans Progressiva** (also known as Fibrodysplasia Ossificans Progressiva - FOP) is a rare genetic disorder characterized by the progressive replacement of soft tissues, such as muscles, tendons, and ligaments, by heterotopic bone. **Why Lung Disease is the Correct Answer:** The primary cause of mortality in FOP is **Thoracic Insufficiency Syndrome**. As the disease progresses, heterotopic ossification involves the intercostal muscles, paravertebral muscles, and the joints of the thoracic cage (ribs and vertebrae). This leads to: 1. **Restrictive Lung Disease:** The chest wall becomes rigid and "frozen," severely limiting expansion during inspiration. 2. **Respiratory Failure:** Reduced vital capacity leads to chronic hypoventilation and eventually cor pulmonale. 3. **Pneumonia:** Inability to cough effectively leads to secretion retention and recurrent life-threatening pulmonary infections. **Analysis of Incorrect Options:** * **Nutritional Deficiency (A):** While ossification of the masseter and jaw muscles can lead to difficulty in eating (starvation risk), it is rarely the primary cause of death compared to respiratory failure. * **Bed Sores (B) & Septicemia (D):** Although patients become severely immobilized, modern nursing care and antibiotics make these less common primary causes of death than the irreversible mechanical restriction of the lungs. **NEET-PG High-Yield Pearls:** * **Genetics:** Autosomal dominant inheritance; mutation in the **ACVR1 gene** (encoding the ALK2 receptor). * **Classic Triad/Sign:** Progressive heterotopic ossification and **congenital malformation of the great toe** (shortened hallux with hallux valgus). * **Management Caution:** Avoid intramuscular injections, biopsies, or surgeries, as trauma "flares up" the condition, leading to rapid new bone formation.

Q: Salmonella osteomyelitis is most common in which of the following conditions?

Sickle cell disease. **Explanation:** **Salmonella osteomyelitis** is a classic association in patients with **Sickle Cell Disease (SCD)**. While *Staphylococcus aureus* remains the most common cause of osteomyelitis in the general population, *Salmonella* species (a Gram-negative rod) show a unique predilection for patients with hemoglobinopathies like SCD. **Why Sickle Cell Disease?** The underlying mechanism involves chronic **vaso-occlusive crises** leading to functional asplenia and intestinal infarctions. These infarctions allow *Salmonella* to translocate from the gut into the bloodstream. Furthermore, infarcted bone marrow provides an ideal ischemic environment for the bacteria to seed and proliferate. **Analysis of Incorrect Options:** * **HIV Infection:** These patients are predisposed to opportunistic infections (e.g., Fungal, Mycobacterial), but *Salmonella* osteomyelitis is not a hallmark feature. * **Intravenous Drug Abuse (IVDA):** IV drug users are at high risk for osteomyelitis, but the most common organisms are *S. aureus* and **Pseudomonas aeruginosa** (often affecting the "S" joints: Spine, Sacroiliac, Symphysis pubis, and Sternoclavicular). * **Pregnancy:** While pregnancy is a state of relative immunosuppression, it does not specifically predispose individuals to *Salmonella* bone infections. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of osteomyelitis in SCD:** *Salmonella* (in many exams) or *S. aureus* (statistically, though *Salmonella* is the "characteristic" answer). * **Most common cause of osteomyelitis overall:** *Staphylococcus aureus*. * **Drug of choice for Salmonella osteomyelitis:** Third-generation cephalosporins (e.g., Ceftriaxone) or Fluoroquinolones. * **Radiology:** Look for "diaphyseal" involvement and symmetrical involvement in SCD patients.

Q: What is the commonest cause of hematogenous osteomyelitis?

Staphylococcus aureus. **Explanation:** **Staphylococcus aureus** is the most common cause of acute hematogenous osteomyelitis across almost all age groups, including children and adults. Its dominance is attributed to its high virulence and specific cell-surface receptors (adhesins) that allow it to bind effectively to bone matrix components like collagen, fibronectin, and laminin. **Analysis of Options:** * **Option B (Staphylococcus aureus):** Correct. It accounts for approximately 70-90% of cases. In children, the infection typically starts in the **metaphysis** of long bones due to the presence of non-anastomosing "hairpin" loops of nutrient arteries where blood flow is sluggish, favoring bacterial seeding. * **Option A (Streptococcus):** While Group B Streptococcus is a significant cause in neonates, it is less common than *S. aureus* in the general population. * **Option C (Salmonella):** This is a high-yield distractor. While *S. aureus* remains common, **Salmonella** is the most characteristic cause of osteomyelitis in patients with **Sickle Cell Anemia**. * **Option D (Haemophilus influenzae):** Previously common in children under age 5, its incidence has drastically declined due to the widespread implementation of the HiB vaccine. **NEET-PG High-Yield Pearls:** 1. **Most common site:** Metaphysis of long bones (Distal Femur > Proximal Tibia). 2. **Drug Users:** *Pseudomonas aeruginosa* is frequently implicated in osteomyelitis involving the spine or fibrocartilaginous joints. 3. **Puncture wounds through footwear:** Often associated with *Pseudomonas*. 4. **Neonates:** *S. aureus*, *E. coli*, and Group B Streptococcus are the primary pathogens. 5. **Investigation of choice:** **MRI** is the most sensitive imaging modality for early diagnosis (detects changes within 48 hours).

Arthrology and Infections Indian Medical PG Practice Questions and MCQs

Question 1: Osteosclerosis of bone occurs due to?

A. Decreased host resistance
B. Increase in the virulence of organisms causing infection
C. Increased host response (Correct Answer)
D. Occurs in immunocompromised patients

Explanation: ### Explanation **Concept Overview:** Osteosclerosis refers to an abnormal increase in bone density, characterized by thickening of the trabeculae and narrowing of the medullary canal. In the context of infections (like chronic osteomyelitis), it represents a **productive or formative bone response** rather than a destructive one. **Why Option C is Correct:** Osteosclerosis occurs when the **host’s immune response is strong** and the infecting organism’s virulence is relatively low. This balance allows the body to contain the infection by stimulating osteoblastic activity, leading to the formation of dense, sclerotic bone. A classic clinical example is **Garré’s Sclerosing Osteomyelitis**, where the body reacts to a low-grade chronic infection by producing massive subperiosteal new bone and sclerosis without significant suppuration or sequestration. **Why Other Options are Incorrect:** * **Options A & D:** Decreased host resistance or an immunocompromised state typically leads to rapid, aggressive bone destruction (osteolysis) and systemic spread, rather than the organized, dense bone formation seen in sclerosis. * **Option B:** High virulence of an organism usually results in acute suppuration, abscess formation, and bone necrosis (sequestrum). Sclerosis is a hallmark of a chronic, low-grade process where the host is "winning" the battle or maintaining a stalemate. **High-Yield Clinical Pearls for NEET-PG:** * **Garré’s Sclerosing Osteomyelitis:** Most common in the mandible and tibia; characterized by "onion-skin" periosteal reaction and dense sclerosis. * **Brodie’s Abscess:** Another form of high host resistance where a subacute infection is localized and walled off by a rim of sclerotic bone. * **Radiological Sign:** On X-ray, osteosclerosis appears as increased radiopacity (whiteness) and loss of the normal trabecular pattern.

Question 2: What is the usual site of tuberculous bursitis?

A. Prepatellar
B. Subacromial
C. Subdeltoid
D. Trochanteric (Correct Answer)

Explanation: ### Explanation **Correct Option: D. Trochanteric** Tuberculous bursitis is a chronic granulomatous inflammation caused by *Mycobacterium tuberculosis*. Among all the bursae in the human body, the **Trochanteric bursa** (located between the greater trochanter and the gluteus maximus/tensor fasciae latae) is the **most common site** of involvement. The pathogenesis usually involves the hematogenous spread of the bacilli or direct extension from an underlying focus of osteomyelitis in the greater trochanter. Clinically, it presents as a "cold abscess" over the lateral aspect of the hip, often associated with a limp and local tenderness, though hip joint movements usually remain preserved in the early stages. **Why other options are incorrect:** * **A. Prepatellar:** While the prepatellar bursa is a common site for *septic* (pyogenic) or *traumatic* bursitis (Housemaid’s knee), it is rarely affected by tuberculosis. * **B & C. Subacromial and Subdeltoid:** These bursae are occasionally involved in TB, often secondary to tuberculosis of the shoulder joint (Caries Sicca), but they are statistically less common than trochanteric involvement. **Clinical Pearls for NEET-PG:** * **Pathognomonic Sign:** The presence of **"Rice bodies"** (fibrin masses) within the bursal fluid is a classic finding in tuberculous bursitis and rheumatoid arthritis. * **Radiology:** X-rays may show soft tissue swelling and irregular erosions of the greater trochanter (the "hidden" primary focus). * **Treatment:** Management involves a combination of Anti-Tubercular Therapy (ATT) and surgical excision (bursectomy) if the disease is extensive or recalcitrant. * **Differential Diagnosis:** Must be distinguished from "Snapping Hip Syndrome" and Trochanteric Pain Syndrome.

Question 3: A 45-year-old patient presents with symptoms of septic arthritis. What is the most common cause in this patient?

A. Gonococcus
B. Staphylococcus aureus (Correct Answer)
C. Salmonella
D. Pneumococci

Explanation: **Explanation:** Septic arthritis is a medical emergency characterized by the infection of a joint space. In adults, the most common route of infection is **hematogenous spread**. **1. Why Staphylococcus aureus is correct:** *Staphylococcus aureus* is the **most common overall cause** of septic arthritis across all age groups (except neonates, where Group B Streptococcus is significant). It is a highly virulent organism that produces proteases, which can lead to rapid joint destruction if not treated promptly. In a 45-year-old patient, unless specific risk factors (like IV drug use or STIs) are mentioned, *S. aureus* remains the statistical primary pathogen. **2. Analysis of Incorrect Options:** * **A. Gonococcus:** *Neisseria gonorrhoeae* is a common cause of septic arthritis in **young, sexually active adults**. It often presents with a triad of tenosynovitis, dermatitis, and polyarthralgia. However, *S. aureus* still holds a higher overall prevalence in the general adult population. * **C. Salmonella:** This is a high-yield association for patients with **Sickle Cell Anemia**. While *S. aureus* is still common in these patients, *Salmonella* is a characteristic and frequently tested pathogen for this specific demographic. * **D. Pneumococci:** *Streptococcus pneumoniae* can cause septic arthritis but is much less common than Staphylococci, usually occurring secondary to pneumonia or meningitis. **High-Yield Clinical Pearls for NEET-PG:** * **Most common joint involved:** Knee joint (>50% of cases). * **Gold Standard Diagnosis:** Arthrocentesis (Joint fluid analysis) showing WBC count >50,000/mm³ with >75% polymorphonuclear cells. * **IV Drug Users:** Increased incidence of infection in fibrocartilaginous joints (Sternoclavicular and Sacroiliac joints); common organisms include *Pseudomonas aeruginosa*. * **Prosthetic Joints:** *Staphylococcus epidermidis* is a frequent culprit.

Question 4: All of the following statements about synovial fluid are true, except-

A. Follows non-Newtonian fluid kinetics
B. Secreted primarily by type A synovial cells (Correct Answer)
C. Contains hyaluronic acid
D. Viscosity is variable

Explanation: ### Explanation **Concept Overview:** Synovial fluid is a ultrafiltrate of blood plasma supplemented with high concentrations of hyaluronic acid. It is produced by the **synovium**, which consists of two distinct types of synoviocytes: **Type A** (macrophage-like) and **Type B** (fibroblast-like) cells. **Why Option B is the Correct Answer (The False Statement):** The primary function of **Type A synoviocytes** is phagocytosis (clearing debris from the joint space). It is the **Type B synoviocytes** that are responsible for the synthesis and secretion of hyaluronic acid and lubricin, which give synovial fluid its unique properties. Therefore, stating that it is secreted primarily by Type A cells is incorrect. **Analysis of Other Options:** * **Option A (Non-Newtonian kinetics):** This is **true**. Synovial fluid does not have a constant viscosity; its flow properties change under pressure. * **Option C (Contains Hyaluronic acid):** This is **true**. Hyaluronic acid is the key component that provides high viscosity and lubrication to the joint. * **Option D (Viscosity is variable):** This is **true**. Due to its non-Newtonian nature (specifically "thixotropic" behavior), the viscosity decreases as the shear rate increases (e.g., during rapid joint movement). **High-Yield Clinical Pearls for NEET-PG:** * **Normal Synovial Fluid:** Clear, straw-colored, high viscosity, and contains <200 WBCs/mm³. * **String Sign:** A test for viscosity; normal fluid forms a 3–5 cm "string" when dropped from a syringe. Viscosity is **decreased** in inflammatory conditions like Rheumatoid Arthritis. * **Mucin Clot Test:** Adding acetic acid to normal synovial fluid forms a tight clot (due to hyaluronic acid). A poor/friable clot indicates inflammation or infection. * **Septic Arthritis:** Characterized by a WBC count typically >50,000/mm³ and low glucose levels.

Question 5: What is the most common cause of bony ankylosis?

A. Rheumatoid arthritis
B. Pyogenic arthritis (Correct Answer)
C. Traumatic arthritis
D. Osteoarthritis

Explanation: **Explanation:** **Bony ankylosis** refers to the complete fusion of a joint due to the proliferation of bone across the joint space, resulting in total loss of movement. **Why Pyogenic Arthritis is the Correct Answer:** Pyogenic (septic) arthritis is the most common cause of bony ankylosis. The underlying mechanism involves the release of proteolytic enzymes by polymorphonuclear leukocytes (neutrophils) and bacteria. These enzymes rapidly destroy the articular cartilage, exposing the subchondral bone. During the healing phase, the intense inflammatory response leads to the formation of a bridge of new bone (callus) across the joint, resulting in permanent osseous fusion. **Analysis of Incorrect Options:** * **Rheumatoid Arthritis (RA):** RA typically leads to **fibrous ankylosis**. While bony fusion can occur (especially in the carpal and tarsal bones), the primary pathology is a chronic proliferative synovitis (pannus) that erodes cartilage but rarely results in complete bony bridge formation compared to pyogenic infections. * **Traumatic Arthritis:** This usually leads to secondary osteoarthritis. While severe intra-articular fractures can lead to fusion, it is statistically less common than infection-induced ankylosis. * **Osteoarthritis (OA):** OA is characterized by the loss of joint space and osteophyte formation, but it **never** results in ankylosis. The joint remains mobile, albeit painful and restricted. **NEET-PG High-Yield Pearls:** * **Pyogenic Arthritis:** Leads to **Bony** ankylosis. * **Tuberculous (TB) Arthritis:** Classically leads to **Fibrous** ankylosis (except in the spine/Pott’s disease, where bony fusion is common). * **Ankylosing Spondylitis:** A classic cause of bony ankylosis of the **axial skeleton** (SI joints and spine). * **Most common organism in Pyogenic Arthritis:** *Staphylococcus aureus* (overall); *Neisseria gonorrhoeae* (sexually active young adults).

Question 6: Choose the wrong statement about osteomyelitis?

A. Sickle cell anemia is associated with Salmonella.
B. HIV infection is associated with Staph aureus.
C. Post surgical infections are commonly caused by Pseudomonas aeruginosa. (Correct Answer)
D. Diabetic ulcers can be caused by Anaerobes.

Explanation: **Explanation:** The correct answer is **C** because it is a factually incorrect statement. In orthopaedic practice, **Staphylococcus aureus** (specifically MRSA or MSSA) remains the most common cause of post-surgical infections and surgical site infections (SSIs). While *Pseudomonas aeruginosa* can cause infections in specific scenarios—such as puncture wounds through sneakers or in intravenous drug users—it is not the primary organism for general post-surgical osteomyelitis. **Analysis of other options:** * **Option A:** Patients with **Sickle Cell Anemia** have an increased susceptibility to **Salmonella** osteomyelitis. This is due to functional asplenia and intestinal infarcts that allow Salmonella to enter the bloodstream and seed in the bone. * **Option B:** Despite the immunocompromised state in **HIV**, **Staphylococcus aureus** remains the most common cause of osteomyelitis, similar to the general population. * **Option D:** **Diabetic foot ulcers** are typically polymicrobial. While *S. aureus* is common, **Anaerobes** (like *Bacteroides*) and Gram-negative bacilli are frequently involved due to the ischemic, necrotic environment of the deep tissues. **High-Yield Clinical Pearls for NEET-PG:** * **Overall most common cause:** *Staphylococcus aureus* (across almost all age groups and categories). * **Drug Abusers:** High incidence of *Pseudomonas* and *Serratia* (often involving the spine or sacroiliac joints). * **Infants/Neonates:** *Group B Streptococcus* and *E. coli* are significant pathogens. * **Puncture wound in foot:** Think *Pseudomonas aeruginosa*. * **Chronic Osteomyelitis pathognomonic features:** *Sequestrum* (dead bone), *Involucrum* (new bone sheath), and *Cloaca* (opening for pus drainage).

Question 7: On X-ray, dead bone appears as:

A. More radiolucent
B. More radiopaque (Correct Answer)
C. With osteophytes growing out
D. Soap-bubble appearance

Explanation: **Explanation:** The correct answer is **B. More radiopaque**. In the context of bone pathology, specifically **Chronic Osteomyelitis**, dead bone is referred to as a **Sequestrum**. It appears more radiopaque (whiter/denser) on an X-ray due to three primary reasons: 1. **Loss of Blood Supply:** Dead bone has no blood flow, preventing the action of osteoclasts. Therefore, it cannot undergo bone resorption. 2. **Relative Sclerosis:** Surrounding living bone undergoes "disuse osteoporosis" (hyperemic decalcification) due to inflammation and lack of use, making the dead bone look denser by comparison. 3. **Physical Changes:** The sequestrum may undergo some physical compression and mineral precipitation, further increasing its density. **Analysis of Incorrect Options:** * **A. More radiolucent:** This indicates bone loss or decreased mineral density, seen in acute infections, tumors, or metabolic bone diseases (osteoporosis). * **C. With osteophytes:** These are bony projections associated with **Osteoarthritis** (degenerative joint disease), not bone death. * **D. Soap-bubble appearance:** This is a classic radiological sign of **Giant Cell Tumor (GCT)** of the bone or occasionally Adamantinoma, characterized by expansive, multiloculated lucent lesions. **NEET-PG High-Yield Pearls:** * **Sequestrum:** Dead bone (Radiopaque). * **Involucrum:** A layer of new living bone formed around the sequestrum (derived from the periosteum). * **Cloaca:** An opening in the involucrum through which pus and sequestra are discharged. * **Brodie’s Abscess:** A form of subacute/chronic osteomyelitis appearing as a radiolucent nidus surrounded by sclerosis, typically in the metaphysis.

Question 8: A 60-year-old person suffering from myositis ossificans progressiva has which of the following as the usual cause of death?

A. Nutritional deficiency
B. Bed sore
C. Lung disease (Correct Answer)
D. Septicemia

Explanation: **Explanation:** **Myositis Ossificans Progressiva** (also known as Fibrodysplasia Ossificans Progressiva - FOP) is a rare genetic disorder characterized by the progressive replacement of soft tissues, such as muscles, tendons, and ligaments, by heterotopic bone. **Why Lung Disease is the Correct Answer:** The primary cause of mortality in FOP is **Thoracic Insufficiency Syndrome**. As the disease progresses, heterotopic ossification involves the intercostal muscles, paravertebral muscles, and the joints of the thoracic cage (ribs and vertebrae). This leads to: 1. **Restrictive Lung Disease:** The chest wall becomes rigid and "frozen," severely limiting expansion during inspiration. 2. **Respiratory Failure:** Reduced vital capacity leads to chronic hypoventilation and eventually cor pulmonale. 3. **Pneumonia:** Inability to cough effectively leads to secretion retention and recurrent life-threatening pulmonary infections. **Analysis of Incorrect Options:** * **Nutritional Deficiency (A):** While ossification of the masseter and jaw muscles can lead to difficulty in eating (starvation risk), it is rarely the primary cause of death compared to respiratory failure. * **Bed Sores (B) & Septicemia (D):** Although patients become severely immobilized, modern nursing care and antibiotics make these less common primary causes of death than the irreversible mechanical restriction of the lungs. **NEET-PG High-Yield Pearls:** * **Genetics:** Autosomal dominant inheritance; mutation in the **ACVR1 gene** (encoding the ALK2 receptor). * **Classic Triad/Sign:** Progressive heterotopic ossification and **congenital malformation of the great toe** (shortened hallux with hallux valgus). * **Management Caution:** Avoid intramuscular injections, biopsies, or surgeries, as trauma "flares up" the condition, leading to rapid new bone formation.

Question 9: Salmonella osteomyelitis is most common in which of the following conditions?

A. Sickle cell disease (Correct Answer)
B. HIV infection
C. Intravenous drug abuse
D. Pregnancy

Explanation: **Explanation:** **Salmonella osteomyelitis** is a classic association in patients with **Sickle Cell Disease (SCD)**. While *Staphylococcus aureus* remains the most common cause of osteomyelitis in the general population, *Salmonella* species (a Gram-negative rod) show a unique predilection for patients with hemoglobinopathies like SCD. **Why Sickle Cell Disease?** The underlying mechanism involves chronic **vaso-occlusive crises** leading to functional asplenia and intestinal infarctions. These infarctions allow *Salmonella* to translocate from the gut into the bloodstream. Furthermore, infarcted bone marrow provides an ideal ischemic environment for the bacteria to seed and proliferate. **Analysis of Incorrect Options:** * **HIV Infection:** These patients are predisposed to opportunistic infections (e.g., Fungal, Mycobacterial), but *Salmonella* osteomyelitis is not a hallmark feature. * **Intravenous Drug Abuse (IVDA):** IV drug users are at high risk for osteomyelitis, but the most common organisms are *S. aureus* and **Pseudomonas aeruginosa** (often affecting the "S" joints: Spine, Sacroiliac, Symphysis pubis, and Sternoclavicular). * **Pregnancy:** While pregnancy is a state of relative immunosuppression, it does not specifically predispose individuals to *Salmonella* bone infections. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of osteomyelitis in SCD:** *Salmonella* (in many exams) or *S. aureus* (statistically, though *Salmonella* is the "characteristic" answer). * **Most common cause of osteomyelitis overall:** *Staphylococcus aureus*. * **Drug of choice for Salmonella osteomyelitis:** Third-generation cephalosporins (e.g., Ceftriaxone) or Fluoroquinolones. * **Radiology:** Look for "diaphyseal" involvement and symmetrical involvement in SCD patients.

Question 10: What is the commonest cause of hematogenous osteomyelitis?

A. Streptococcus
B. Staphylococcus aureus (Correct Answer)
C. Salmonella
D. Haemophilus influenza

Explanation: **Explanation:** **Staphylococcus aureus** is the most common cause of acute hematogenous osteomyelitis across almost all age groups, including children and adults. Its dominance is attributed to its high virulence and specific cell-surface receptors (adhesins) that allow it to bind effectively to bone matrix components like collagen, fibronectin, and laminin. **Analysis of Options:** * **Option B (Staphylococcus aureus):** Correct. It accounts for approximately 70-90% of cases. In children, the infection typically starts in the **metaphysis** of long bones due to the presence of non-anastomosing "hairpin" loops of nutrient arteries where blood flow is sluggish, favoring bacterial seeding. * **Option A (Streptococcus):** While Group B Streptococcus is a significant cause in neonates, it is less common than *S. aureus* in the general population. * **Option C (Salmonella):** This is a high-yield distractor. While *S. aureus* remains common, **Salmonella** is the most characteristic cause of osteomyelitis in patients with **Sickle Cell Anemia**. * **Option D (Haemophilus influenzae):** Previously common in children under age 5, its incidence has drastically declined due to the widespread implementation of the HiB vaccine. **NEET-PG High-Yield Pearls:** 1. **Most common site:** Metaphysis of long bones (Distal Femur > Proximal Tibia). 2. **Drug Users:** *Pseudomonas aeruginosa* is frequently implicated in osteomyelitis involving the spine or fibrocartilaginous joints. 3. **Puncture wounds through footwear:** Often associated with *Pseudomonas*. 4. **Neonates:** *S. aureus*, *E. coli*, and Group B Streptococcus are the primary pathogens. 5. **Investigation of choice:** **MRI** is the most sensitive imaging modality for early diagnosis (detects changes within 48 hours).

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