Septic Arthritis — MCQs
A child presents with painful limp and restricted hip rotation. ESR and CRP are elevated. Initial plain radiograph is normal. What is the next best imaging study?
Which of the following is an orthopedic emergency?
In acute septic arthritis of hip in children, which finding indicates poor prognosis?
All are features of septic arthritis except:
What will the aspirated synovial fluid in a case of septic arthritis typically show?
Windswept deformity is seen in which condition?
Osteosclerosis of bone occurs due to?
What is the usual site of tuberculous bursitis?
A 45-year-old patient presents with symptoms of septic arthritis. What is the most common cause in this patient?
All of the following statements about synovial fluid are true, except-
Septic Arthritis Indian Medical PG Practice Questions and MCQs
Question 1: A child presents with painful limp and restricted hip rotation. ESR and CRP are elevated. Initial plain radiograph is normal. What is the next best imaging study?
- A. CT Scan
- B. MRI with contrast (Correct Answer)
- C. Bone Scan
- D. Plain Radiograph
Explanation: ***MRI with contrast*** - An **MRI with contrast** is the most sensitive and specific imaging modality for detecting early changes in **osteomyelitis** or **septic arthritis**, which are serious conditions given the child's symptoms and elevated inflammatory markers. - It can visualize soft tissue and bone marrow edema, joint effusions, and abscesses, guiding immediate treatment. *CT Scan* - While useful for bony detail, a CT scan is **less sensitive than MRI** for detecting early bone marrow changes or soft tissue inflammation in the hip joint. - It also involves **radiation exposure**, which should be limited in children when other effective modalities are available. *Bone Scan* - A bone scan using **technetium-99m** is sensitive for detecting increased bone turnover, but it is **not specific for infection** and cannot differentiate between inflammatory processes, tumors, or fractures. - It provides less anatomical detail compared to MRI, making precise localization of an infection more challenging. *Plain Radiograph* - Plain radiographs are typically the **initial imaging study** for orthopedic complaints but are often **normal in early stages** of septic arthritis or osteomyelitis. - Significant radiographic changes, such as bone erosion or joint space widening, usually appear much later in the disease process.
Question 2: Which of the following is an orthopedic emergency?
- A. Intraarticular fracture
- B. Septic arthritis (Correct Answer)
- C. Fracture lateral condyle humerus
- D. Fracture neck femur
Explanation: ***Septic arthritis*** - This is an **orthopedic emergency** due to the rapid destruction of cartilage and bone if not treated promptly. - It requires urgent **surgical washout** and intravenous antibiotics to prevent irreversible joint damage and systemic infection. *Intraarticular fracture* - While requiring careful management to optimize joint function, an **intraarticular fracture** is typically not an immediate emergency unless there's associated neurovascular compromise or compartment syndrome. - Surgical intervention can often be planned within a certain timeframe (days) rather than hours. *Fracture lateral condyle humerus* - This fracture in children is significant due to potential for non-union or avascular necrosis, but it is not considered an immediate **life- or limb-threatening emergency**. - Management usually involves **reduction and fixation** but does not carry the same degree of urgency as active joint infection. *Fracture neck femur* - A fractured neck of femur requires surgical intervention to prevent complications like **avascular necrosis** and optimize mobility, particularly in elderly patients. - While serious, it primarily presents a risk of long-term disability and complications, not an immediate destructive process like septic arthritis.
Question 3: In acute septic arthritis of hip in children, which finding indicates poor prognosis?
- A. Age <2 years
- B. Delay in Treatment >48 hours (Correct Answer)
- C. Elevated CRP
- D. Gram Negative Infection
Explanation: ***Delay in Treatment >48 hours*** - A delay in treatment of **acute septic hip arthritis** beyond 48 hours significantly increases the risk of irreversible cartilage damage and long-term functional impairment due to sustained inflammatory and enzymatic degradation. - This delay can lead to more severe joint destruction, avascular necrosis of the femoral head, and post-infectious osteoarthritis, all contributing to a **poor prognosis**. *Age <2 years* - While younger children can have more subtle symptoms and a higher risk of diagnostic delay, age itself is not the most determinant factor for poor prognosis compared to treatment delay. - Management in this age group focuses on early diagnosis and aggressive treatment to prevent growth plate damage. *Elevated CRP* - **Elevated C-reactive protein (CRP)** is a common finding in acute septic arthritis, indicating systemic inflammation and the severity of infection. - While reflecting disease activity, an elevated CRP alone does not directly indicate poor prognosis as it typically responds well to appropriate antibiotic treatment and surgical drainage. *Gram Negative Infection* - Gram-negative infections can be more challenging to treat and may require specific antibiotic regimens, but the type of organism is generally less critical than the **duration of untreated infection** in determining long-term outcomes. - With prompt and appropriate therapy, many gram-negative infections can be successfully managed without causing poor long-term outcomes.
Question 4: All are features of septic arthritis except:
- A. Joint swelling
- B. Symmetric joint involvement (Correct Answer)
- C. Painful joint movement
- D. Elevated ESR
Explanation: Symmetric joint involvement - Septic arthritis typically presents as a monoarticular condition [1], affecting a single joint, or sometimes a few joints in an asymmetric pattern. - Symmetrical joint involvement is more characteristic of inflammatory arthropathies like rheumatoid arthritis, not septic arthritis [1]. Joint swelling - Inflammation and the accumulation of effusion in the joint capsule due to infection commonly lead to noticeable joint swelling. - This is a hallmark symptom as the body responds to bacterial invasion within the joint space. Painful joint movement - The acute inflammatory process and distension of the joint capsule by infection cause significant pain with any movement or weight-bearing. - Patients often present with an unwillingness to move the affected joint, characteristic of a "pseudoparalysis". Elevated ESR - Erythrocyte sedimentation rate (ESR) is a general marker of inflammation and is typically significantly elevated in septic arthritis due to the systemic inflammatory response to infection. - This indicator helps confirm the presence of an active inflammatory process, though it is not specific to septic arthritis.
Question 5: What will the aspirated synovial fluid in a case of septic arthritis typically show?
- A. Clear and straw-colored fluid
- B. Low viscosity fluid
- C. Cloudy or purulent fluid
- D. Markedly increased polymorphonuclear leukocytes (Correct Answer)
Explanation: ***Markedly increased polymorphonuclear leukocytes*** - **Septic arthritis** is characterized by an acute infection within the joint, leading to a profound inflammatory response with a significant influx of **neutrophils** (polymorphonuclear leukocytes) into the synovial fluid. - A synovial leukocyte count greater than **50,000 cells/mm³** with over **75% neutrophils** is highly suggestive of septic arthritis. *Clear and straw-colored fluid* - This description typically corresponds to **normal synovial fluid** or fluid from a mild **non-inflammatory condition**, which is not consistent with bacterial infection. - Normal synovial fluid is usually **transparent**, indicating the absence of significant cellular debris or inflammatory cells. *Low viscosity fluid* - While septic synovial fluid can have reduced viscosity due to the breakdown of **hyaluronic acid** by bacterial enzymes and inflammatory mediators, this characteristic alone is not the most definitive diagnostic feature. - Reduced viscosity is also observed in other inflammatory conditions, making it less specific than direct cellular analysis for diagnosing infection. *Cloudy or purulent fluid* - The presence of **cloudy** or **purulent (pus-like)** fluid *is* often seen in septic arthritis, reflecting the high cell count and protein content. - However, this is a **gross visual observation**, and a more precise and diagnostic indicator is the microscopic finding of markedly increased **polymorphonuclear leukocytes**.
Question 6: Windswept deformity is seen in which condition?
- A. Hyperparathyroidism
- B. Scurvy
- C. Rheumatoid Arthritis
- D. Rickets (Correct Answer)
Explanation: ***Rickets*** - **Windswept deformity** is characterized by bilateral knee deformities where one knee is in **valgus** and the other is in **varus**. - This condition is caused by a deficiency in **vitamin D**, **calcium**, or **phosphate**, leading to improper bone mineralization and subsequent bone deformities. *Rheumatoid Arthritis* - Rheumatoid arthritis is a **chronic autoimmune inflammatory disease** primarily affecting the synovial joints. - While it can cause joint deformities, they typically involve symmetric joint swelling, pain, and stiffness, with characteristic deformities like **ulnar deviation** or **swan-neck deformities**, rather than windswept deformity. *Hyperparathyroidism* - Hyperparathyroidism leads to excessive production of **parathyroid hormone**, which causes increased bone resorption and elevated blood calcium levels. - It can result in bone fragility, **osteitis fibrosa cystica**, and kidney stones, but it does not cause specific windswept deformity. *Scurvy* - Scurvy results from a severe deficiency of **vitamin C**, which is essential for collagen synthesis. - It presents with symptoms like bleeding gums, poor wound healing, and perifollicular hemorrhages, but it does not typically cause windswept deformity of the knees.
Question 7: 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 8: 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 9: 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 10: 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.
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