Arthrology and Infections Practice Questions

Q: What is the commonest cause of acute osteomyelitis?

Hematogenous route. **Explanation:** **Hematogenous route (Option D)** is the most common cause of acute osteomyelitis, particularly in the pediatric population. This occurs when bacteria (most commonly *Staphylococcus aureus*) enter the bloodstream from a distant site (like a skin boil or sore throat) and settle in the **metaphysis** of long bones. The metaphysis is the preferred site due to its high vascularity and the presence of "hairpin loops" in the capillary bed, which lead to sluggish blood flow, allowing bacteria to settle and proliferate. **Analysis of Incorrect Options:** * **Trauma (Option A):** While open fractures or deep soft tissue injuries can lead to "Direct Inoculation Osteomyelitis," it is statistically less common than the hematogenous spread in the general population. * **Surgery (Option B):** Post-operative infections (e.g., after ORIF or joint replacement) are significant causes of *chronic* or *iatrogenic* osteomyelitis but do not represent the primary etiology of acute cases globally. * **Fungal infection (Option C):** Fungal osteomyelitis is rare and typically seen only in immunocompromised patients or those on long-term parenteral nutrition. **High-Yield Clinical Pearls for NEET-PG:** * **Most common organism:** *Staphylococcus aureus* (overall). * **Most common organism in Sickle Cell Anemia:** *Salmonella* (though *S. aureus* remains a close second). * **Most common site:** Metaphysis of long bones (Distal Femur > Proximal Tibia). * **Earliest X-ray sign:** Soft tissue swelling (seen at 3–5 days). Bony changes (periosteal reaction/rarefaction) take **10–14 days** to appear. * **Investigation of choice:** **MRI** (most sensitive for early diagnosis).

Q: Which of the following is true about acute osteomyelitis?

Severe pain.. **Explanation:** Acute Hematogenous Osteomyelitis (AHO) is a surgical emergency primarily seen in children. The correct answer is **Severe pain** because it is the most consistent and earliest clinical feature. 1. **Why "Severe Pain" is correct:** The infection typically starts in the **metaphysis** of long bones. As pus accumulates within the rigid medullary cavity, the intraosseous pressure rises significantly. This pressure stretches the sensitive periosteum, leading to excruciating, throbbing pain and exquisite point tenderness. This is often the "earliest" sign before systemic symptoms or radiological changes appear. 2. **Why other options are incorrect:** * **Option A:** While it is a classic teaching that X-rays are negative for 10–14 days, modern digital radiography can sometimes detect subtle soft tissue swelling or periosteal reactions slightly earlier (around 7–10 days). However, "cannot be detected" is an absolute statement that is less clinically definitive than the presence of pain. * **Option C:** While there is "pseudoparalysis" (the patient refuses to move the limb due to pain), the **joint movements** themselves are usually preserved if the joint is moved passively and gently. This helps differentiate it from Septic Arthritis, where any movement is impossible. * **Option D:** Bone scans (Technetium-99m) are highly sensitive and can detect increased uptake within **24 to 48 hours** of infection. Waiting 2 weeks would lead to irreversible bone necrosis (sequestrum). **NEET-PG High-Yield Pearls:** * **Most common site:** Metaphysis (due to hairpin bends of vessels and sluggish blood flow). * **Most common organism:** *Staphylococcus aureus*. * **Investigation of choice:** **MRI** (most sensitive and specific for early diagnosis). * **Earliest X-ray sign:** Soft tissue swelling and blurring of fat planes. * **Earliest Bone sign on X-ray:** Periosteal reaction (takes 10–14 days).

Q: An 8-year-old boy presents with a gradually progressing swelling and pain over the upper tibia for 6 months. An X-ray shows a lytic lesion with sclerotic margins in the upper tibial metaphysis. What is the most likely diagnosis?

Brodie's abscess. **Explanation:** The clinical presentation and radiological findings point towards **Brodie’s abscess**, which is a form of **subacute or chronic osteomyelitis**. **Why Brodie’s Abscess is Correct:** Brodie’s abscess is a localized pyogenic abscess within the bone, typically caused by *Staphylococcus aureus*. It characteristically presents in children and young adults with a long-standing (chronic), dull aching pain and swelling. Radiologically, it appears as a **well-defined lytic lesion** surrounded by a **sclerotic (radio-opaque) margin**, representing the body's attempt to wall off the infection. It most commonly affects the **metaphysis** of long bones, particularly the tibia. **Why Other Options are Incorrect:** * **Osteogenic Sarcoma:** While it occurs in the metaphysis of children, it typically presents with a rapidly progressing mass, a "sunburst" periosteal reaction, or Codman’s triangle, rather than a well-defined sclerotic lytic lesion. * **Osteoclastoma (Giant Cell Tumor):** This is an **epiphyseal** lesion that occurs in skeletally mature individuals (20–40 years). It has a characteristic "soap bubble" appearance and lacks a sclerotic rim. * **Ewing’s Sarcoma:** This typically involves the **diaphysis** of long bones and presents with a characteristic "onion-skin" periosteal reaction. **High-Yield NEET-PG Pearls:** * **Most common site:** Upper end of Tibia (Metaphysis). * **Most common organism:** *Staphylococcus aureus*. * **Pathognomonic X-ray finding:** A radiolucent nidus >1 cm with a surrounding zone of reactive sclerosis. * **Treatment:** Surgical curettage and antibiotics. If the lesion is small and asymptomatic, conservative management may be considered.

Q: What is the most common site of tuberculosis of the spine?

Dorsolumbar region. **Explanation:** Tuberculosis of the spine (Pott’s disease) is the most common form of skeletal tuberculosis. The **Dorsolumbar region (T12–L1)** is the most frequently affected site. This is primarily because this region represents a transitional zone where the relatively rigid thoracic spine meets the highly mobile lumbar spine, making it subject to significant mechanical stress. Additionally, the rich vascular supply via the paravertebral venous plexus (Batson’s plexus) facilitates the hematogenous spread of *Mycobacterium tuberculosis* to this area. **Analysis of Options:** * **Dorsolumbar region (Correct):** Statistically the most common site (specifically T12 and L1). It is the junctional area most prone to weight-bearing stress and infection. * **Dorsal/Thoracic region:** The second most common site. While common in children, it is less frequent than the dorsolumbar junction in the general population. * **Lumbar region:** Frequently involved, but usually as an extension or secondary to dorsolumbar involvement. * **Lumbosacral region:** A relatively rare site for primary spinal TB compared to the segments above it. **Clinical Pearls for NEET-PG:** * **Initial Site of Infection:** Usually the **paradiscal** region (anterior part of the vertebral body near the disc). * **Earliest Sign on X-ray:** Reduction/narrowing of the **intervertebral disc space**. * **Cold Abscess:** A hallmark of spinal TB; in the lumbar region, it often tracks down the psoas muscle sheath (Psoas abscess). * **Deformity:** The destruction of the anterior vertebral body leads to wedge collapse, resulting in **Kyphosis** (Gibbus deformity). * **Neurological Deficit:** Pott’s paraplegia is most common when the **upper dorsal spine** is involved due to the narrow canal diameter in that region.

Q: In which of the following conditions dactylitis cannot be seen?

Beta thalassemia. **Explanation:** **Dactylitis**, commonly known as "sausage digit," is the uniform swelling of a finger or toe resulting from inflammation of the small bones, tendons, and surrounding soft tissues. **Why Beta Thalassemia is the correct answer:** In **Beta Thalassemia**, the primary pathology is ineffective erythropoiesis and chronic hemolysis leading to expansion of the bone marrow. While this causes skeletal changes (like the "crew-cut" appearance on skull X-ray or "chipmunk facies"), it **does not** cause acute inflammation or infarction of the phalanges. Therefore, dactylitis is not a clinical feature of Beta Thalassemia. **Analysis of Incorrect Options:** * **Sickle Cell Anaemia:** This is the most common cause of dactylitis in infants (Hand-Foot Syndrome). It occurs due to **vaso-occlusive crises** leading to infarcts in the small bones of the hands and feet. * **Congenital Syphilis:** It causes **syphilitic dactylitis**, characterized by painless, symmetrical swelling of the proximal phalanges due to periostitis. * **Tuberculosis:** Known as **Spina Ventosa**, TB dactylitis involves a cold abscess and cystic expansion of the short tubular bones, usually seen in children. **NEET-PG High-Yield Pearls:** 1. **Spina Ventosa:** The classic radiological sign of TB dactylitis (subperiosteal new bone formation with internal bone destruction). 2. **Spondyloarthropathies:** Dactylitis is a hallmark feature of **Psoriatic Arthritis** (most common), Ankylosing Spondylitis, and Reactive Arthritis. 3. **Sarcoidosis:** Can also cause dactylitis, often presenting with a "lace-like" pattern on X-ray. 4. **Hand-Foot Syndrome:** In Sickle Cell, this is often the first clinical manifestation of the disease in early childhood.

Q: Dawbarn sign is seen in which of the following conditions?

Subacromial bursitis. **Explanation:** **Dawbarn’s Sign** is a classic clinical test used to diagnose **Subacromial Bursitis**. The underlying medical concept relies on the anatomical location of the subacromial bursa, which lies between the acromion process and the rotator cuff. * **Why it is correct:** In a patient with subacromial bursitis, there is a localized point of exquisite tenderness just below the acromion process when the arm is by the side. When the arm is **abducted**, the deltoid muscle contracts and the bursa slides beneath the acromion. This "hides" the inflamed bursa under the bone, protecting it from the examiner's finger, which results in the **disappearance of tenderness**. This disappearance of pain upon abduction is a positive Dawbarn’s sign. **Analysis of Incorrect Options:** * **Infraspinatus tendinitis:** Presents with pain during resisted external rotation; it does not demonstrate the specific disappearance of tenderness characteristic of Dawbarn’s sign. * **Achilles tendon injury:** This involves the ankle. Clinical tests include the Simmonds/Thompson test (calf squeeze). * **Rotator cuff tear:** While often associated with bursitis, a tear typically presents with weakness in abduction (Drop Arm test) and a painful arc, but not the specific "vanishing tenderness" of Dawbarn’s sign. **High-Yield Clinical Pearls for NEET-PG:** * **Painful Arc Syndrome:** Pain felt between 60°–120° of abduction; seen in both subacromial bursitis and supraspinatus tendinitis. * **Neer’s and Hawkins-Kennedy Tests:** Used to identify shoulder impingement syndrome. * **Ludington’s Test:** Used to detect a rupture of the long head of the biceps tendon.

Q: In bony ankylosis, what is characteristically observed?

Painless, no movement. **Explanation:** **Understanding Bony Ankylosis:** Ankylosis refers to the stiffness or fixation of a joint. **Bony ankylosis** (true ankylosis) occurs when there is a complete bridge of bone across the joint space, obliterating the joint cavity. Because the joint is replaced by solid bone, there is **zero movement**. Since pain in joint pathologies usually arises from friction between damaged surfaces or stretching of the capsule during movement, the total lack of motion in bony ankylosis results in a **painless** state. This is commonly seen in the late stages of Septic Arthritis or Ankylosing Spondylitis. **Analysis of Options:** * **Option A (Correct):** Bony fusion prevents all mechanical friction and stress on the joint receptors, leading to a painless, immobile joint. * **Option B & C:** These are incorrect because "complete movement" contradicts the definition of ankylosis (fixation). * **Option D:** This describes **Fibrous Ankylosis**. In fibrous ankylosis, the joint is held together by tough fibrous tissue rather than bone. This allows for slight, restricted movement which is typically **painful** because the underlying disease process is often still active or the fibrous bands are being stretched. **High-Yield Clinical Pearls for NEET-PG:** * **Bony Ankylosis:** No movement, Painless. (Classic cause: Pyogenic/Septic arthritis). * **Fibrous Ankylosis:** Restricted/Incomplete movement, Painful. (Classic cause: Tuberculous arthritis). * **Radiological Sign:** In bony ankylosis, trabeculae can be seen crossing the joint space on an X-ray. * **Management:** If the joint is fixed in a non-functional position, an osteotomy or arthroplasty may be required to restore function.

Q: What are the characteristics of aspirated synovial fluid in septic arthritis?

Markedly increased polymorphonuclear leukocytes. In septic arthritis, the synovial fluid undergoes dramatic changes due to the intense inflammatory response triggered by a bacterial infection. ### **Explanation of the Correct Answer** **Option C (Markedly increased polymorphonuclear leukocytes)** is correct because the hallmark of septic arthritis is a massive influx of neutrophils (PMNs) into the joint space. In a typical septic joint, the White Blood Cell (WBC) count is usually **>50,000 cells/mm³**, with **>75% (often >90%) being polymorphonuclear leukocytes**. This occurs as the body’s primary defense mechanism to phagocytose the invading pathogens. ### **Analysis of Incorrect Options** * **Option A (Clear color):** Incorrect. Normal synovial fluid is straw-colored and transparent. In septic arthritis, the fluid becomes **opaque, turbid, or purulent** due to the high concentration of WBCs, bacteria, and cellular debris. * **Option B (High viscosity):** Incorrect. Normal synovial fluid has high viscosity due to hyaluronan. In infection, bacterial enzymes (like hyaluronidase) and lysosomal enzymes from neutrophils break down hyaluronic acid, resulting in **low viscosity** (the fluid "watery" and does not form a long string). ### **NEET-PG High-Yield Pearls** * **Gold Standard Diagnosis:** Synovial fluid analysis (Gram stain and Culture). * **Glucose Levels:** Characteristically **low** (<60% of serum glucose) because bacteria and WBCs consume glucose. * **Lactate Levels:** Typically **elevated** in septic joints. * **Commonest Organism:** *Staphylococcus aureus* is the overall most common cause; *Neisseria gonorrhoeae* is common in sexually active young adults. * **Emergency Status:** Septic arthritis is an orthopedic emergency because proteolytic enzymes can destroy articular cartilage within 48 hours.

Q: Multiple loose bodies are seen in which of the following conditions?

Osteochondritis dissecans. **Explanation:** **Osteochondritis Dissecans (OCD)** is the most common cause of multiple loose bodies in a joint. It is a pathological process where a localized segment of articular cartilage and underlying subchondral bone separates from the joint surface due to aseptic necrosis. This fragment eventually detaches, becoming a "loose body" (joint mouse). It most commonly affects the lateral aspect of the medial femoral condyle. **Analysis of Options:** * **Osteochondritis Dissecans (Correct):** Characterized by the separation of osteochondral fragments. While it can present with a single fragment, it is the classic textbook answer for the primary cause of multiple loose bodies. * **Synovial Chondromatosis:** This is a benign metaplasia where the synovium produces numerous cartilaginous nodules. While it produces the *highest number* of loose bodies (often hundreds of "snowstorm" appearances), in standard orthopedic nomenclature and MCQ patterns, OCD remains the primary clinical association for "multiple loose bodies" unless "innumerable" or "synovial origin" is specified. * **Osteoarthritis:** May result in loose bodies due to the breaking off of marginal osteophytes, but these are usually few and secondary to the degenerative process. * **Rheumatoid Arthritis:** Loose bodies are rare; joint symptoms are primarily due to synovial pannus and symmetrical joint space narrowing. **High-Yield Clinical Pearls for NEET-PG:** * **Most common site for OCD:** Lateral aspect of the Medial Femoral Condyle (L-MFC). * **Wilson’s Sign:** Positive in OCD of the knee (pain on internal rotation of the tibia during extension, relieved by external rotation). * **Rice Bodies:** Specifically associated with **Tuberculous Arthritis** or Rheumatoid Arthritis (fibrin masses), not to be confused with osteochondral loose bodies. * **Imaging:** MRI is the gold standard for assessing the stability of the fragment.

Question 1

What is the commonest cause of acute osteomyelitis?

Accepted Answer

Hematogenous route

Answer

Trauma

Answer

Surgery

Answer

Fungal infection

Question 2

A patient with HIV is on therapy with protease inhibitors. He presents with limitation of abduction and internal rotation of the hip. What is the most probable diagnosis?

Accepted Answer

Avascular necrosis (AVN) of the femoral head

Answer

Tuberculosis of the hip joint

Answer

Secondary osteoarthritis of the hip

Answer

Septic arthritis of the hip

Question 3

Which of the following is true about acute osteomyelitis?

Accepted Answer

Severe pain.

Answer

Cannot be detected by X-ray before 2 weeks.

Answer

Limitation of movements.

Answer

Bone scan detects after 2 weeks.

Question 4

An 8-year-old boy presents with a gradually progressing swelling and pain over the upper tibia for 6 months. An X-ray shows a lytic lesion with sclerotic margins in the upper tibial metaphysis. What is the most likely diagnosis?

Accepted Answer

Brodie's abscess

Answer

Osteogenic sarcoma

Answer

Osteoclastoma

Answer

Ewing's sarcoma

Question 5

What is the most common site of tuberculosis of the spine?

Accepted Answer

Dorsolumbar region

Answer

Dorsal region

Answer

Lumbar region

Answer

Lumbosacral region

Question 6

In which of the following conditions dactylitis cannot be seen?

Accepted Answer

Beta thalassemia

Answer

Sickle cell anaemia

Answer

Congenital syphilis

Answer

Tuberculosis

Question 7

Dawbarn sign is seen in which of the following conditions?

Accepted Answer

Subacromial bursitis

Answer

Infraspinatus tendinitis

Answer

Achilles tendon injury

Answer

Rotator cuff tear

Question 8

In bony ankylosis, what is characteristically observed?

Accepted Answer

Painless, no movement

Answer

Painful complete movement

Answer

Painless complete movement

Answer

Painful incomplete movement

Question 9

What are the characteristics of aspirated synovial fluid in septic arthritis?

Accepted Answer

Markedly increased polymorphonuclear leukocytes

Answer

Clear color

Answer

High viscosity

Answer

None of the above

Question 10

Multiple loose bodies are seen in which of the following conditions?

Accepted Answer

Osteochondritis dissecans

Answer

Synovial chondromatosis

Answer

Osteoarthritis

Answer

Rheumatoid arthritis

Arthrology and Infections — MCQs

Arthrology and Infections — MCQs

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