Arthrology and Infections Practice Questions

Q: An 18-month-old girl presents with a fever of 104 extdegree F and refusal to walk since waking up. A hip x-ray reveals subtle widening of the left hip joint space. What is the most appropriate initial management?

Surgical drainage of the hip joint. **Explanation:** The clinical presentation of high-grade fever (104°F), refusal to walk (pseudoparalysis), and subtle widening of the hip joint space on X-ray in an 18-month-old is a classic description of **Septic Arthritis of the hip**. **Why Surgical Drainage is Correct:** Septic arthritis of the hip is a **surgical emergency**. The hip joint is a "constrained" joint with an intra-articular femoral neck. Increased intra-articular pressure from pus accumulation can tamponade the retinacular vessels, leading to **Avascular Necrosis (AVN)** of the femoral head within hours. Immediate surgical drainage (arthrotomy or ultrasound-guided aspiration) is mandatory to decompress the joint, evacuate the purulent material, and prevent permanent joint destruction. **Why Other Options are Incorrect:** * **A. Close observation:** This is contraindicated. Delaying treatment in septic arthritis leads to irreversible cartilage damage and hip dislocation. * **B & D. IV Antibiotics (Ceftriaxone/Oxacillin):** While antibiotics are a crucial part of management, they cannot effectively penetrate an undrained, pressurized abscess (the joint). **Drainage must precede or occur concurrently with the initiation of antibiotics.** **NEET-PG High-Yield Pearls:** * **Most common site:** Knee (overall), but the **Hip** is most critical in infants due to the risk of AVN. * **Most common organism:** *Staphylococcus aureus* (overall); *Streptococcus agalactiae* (neonates). * **Kocher’s Criteria:** Used to differentiate septic arthritis from transient synovitis (Non-weight bearing, ESR >40, Fever >38.5°C, WBC >12,000). * **Diagnosis:** Joint aspiration (Arthrocentesis) is the gold standard for diagnosis (WBC count typically >50,000/mm³).

Q: A patient with severe arthritis suddenly becomes unable to move his arms or legs. He is admitted to the neurology floor, but his quadriplegia does not improve with time. If the quadriplegia is due to his arthritis, which of the following types of arthritis does this patient most likely have?

Rheumatoid arthritis. **Explanation:** The correct answer is **Rheumatoid Arthritis (RA)**. The underlying medical concept here is **Atlanto-axial Subluxation (AAS)**. In Rheumatoid Arthritis, chronic inflammation (synovitis) affects the synovial joints of the cervical spine, particularly the **atlanto-axial joint (C1-C2)**. The transverse ligament of the atlas, which holds the odontoid process (dens) of C2 in place, undergoes inflammatory erosion and laxity. This leads to instability and potential subluxation. If the dens displaces posteriorly, it can compress the spinal cord, resulting in sudden-onset **quadriplegia** or even sudden death due to respiratory center compression. **Why other options are incorrect:** * **Ankylosing Spondylitis:** While it involves the spine, it typically causes "bony fusion" (ankylosis) rather than instability. While fractures can occur in a "bamboo spine," spontaneous atlanto-axial subluxation leading to quadriplegia is classic for RA. * **Gouty Arthritis:** This is a metabolic arthropathy primarily affecting peripheral joints (like the 1st MTP joint). It rarely involves the cervical spine or causes cord compression. * **Osteoarthritis:** This is a degenerative condition. While it can cause cervical spondylosis and gradual myelopathy, it does not typically cause the sudden, catastrophic instability seen in RA. **High-Yield Clinical Pearls for NEET-PG:** * **Radiology:** AAS is diagnosed on lateral cervical X-rays in **flexion**; an **Atlantodental Interval (ADI) >3 mm** in adults is significant. * **Pre-operative Caution:** Patients with RA must undergo cervical spine X-rays before any surgery requiring intubation to avoid fatal cord compression during neck extension. * **Involvement:** RA involves the cervical spine but characteristically **spares** the lumbar spine.

Q: Which of the following crystals may give rise to pseudo-neuropathic arthropathy resembling Charcot's joint?

Calcium pyrophosphate dihydrate. **Explanation:** **Calcium Pyrophosphate Dihydrate (CPPD)** deposition disease is a multifaceted crystal arthropathy. While it most commonly presents as "Pseudogout," it can manifest in several clinical patterns. One specific, severe form is **Pseudo-neuropathic arthropathy**. In this variant, the rapid and extensive destruction of the joint (most commonly the knee or hip) mimics the clinical and radiological appearance of a **Charcot’s Joint**. Unlike true Charcot’s joint, which is secondary to loss of sensation (e.g., Diabetes, Syphilis), CPPD-induced arthropathy occurs in the presence of intact neurological function. **Analysis of Incorrect Options:** * **A. Monosodium Urate (MSU):** These crystals cause Gout. While chronic tophaceous gout can lead to joint erosion and "punched-out" lesions, it does not typically mimic the rapid, disorganized joint destruction seen in neuropathic arthropathy. * **B. Hydroxyapatite:** These crystals are associated with calcific tendonitis and "Milwaukee Shoulder." While destructive, the term "pseudo-neuropathic" is classically reserved for CPPD. * **C. Calcium Oxalate:** These crystals are primarily seen in patients with primary oxalosis or those on long-term hemodialysis; they do not present with a Charcot-like joint destruction. **High-Yield Clinical Pearls for NEET-PG:** * **Radiological Hallmark:** The presence of **Chondrocalcinosis** (linear calcification of articular cartilage or fibrocartilage, like the meniscus). * **Crystal Morphology:** CPPD crystals are **weakly positively birefringent** and **rhomboid-shaped** under polarized microscopy. * **Metabolic Associations:** Always screen for "The 3 H's": **H**yperparathyroidism, **H**emochromatosis, and **H**ypomagnesemia. * **Common Site:** The **Knee** is the most common joint involved in CPPD.

Q: What is symphalangism?

Fusion of the interphalangeal joints. **Explanation:** **Symphalangism** refers to the **congenital ankylosis (fusion) of the interphalangeal joints** of the fingers or toes. It occurs due to a failure of the joint space to differentiate during fetal development. It is most commonly seen in the proximal interphalangeal (PIP) joints and is often inherited as an autosomal dominant trait. **Analysis of Options:** * **Option B (Correct):** Symphalangism is derived from the Greek words *syn* (together) and *phalanges*. It specifically describes the end-to-end fusion of phalanges within a single digit, leading to a loss of joint motion. * **Option A (Incorrect):** Reduplication of fingers is known as **Polydactyly**. * **Option C (Incorrect):** Shortening of the fingers due to small phalanges is known as **Brachydactyly**. * **Option D (Incorrect):** Joined or webbed fingers (fusion of adjacent digits) is known as **Syndactyly**. **High-Yield Clinical Pearls for NEET-PG:** * **Cushing’s Symphalangism:** A specific syndrome where symphalangism is associated with hearing loss (stapes fixation). * **Radiological Sign:** On X-ray, the joint space is absent, and there is continuous bony trabeculation across the phalanges. * **Associated Conditions:** It is frequently seen in syndromes like **Apert syndrome** (which also features craniosynostosis and syndactyly). * **Clinical Presentation:** Patients present with "stiff" fingers and an absence of normal skin creases over the affected joints.

Q: What are the potential complications of acute osteomyelitis?

Sepsis. **Explanation:** Acute osteomyelitis is a pyogenic infection of the bone, most commonly caused by *Staphylococcus aureus*. In the acute phase, the primary concern is the systemic spread of the infection. **Why Sepsis is the Correct Answer:** The hallmark of acute osteomyelitis, especially in children, is hematogenous spread. Bacteria from the bone marrow can easily enter the systemic circulation, leading to **sepsis**, septic shock, and multi-organ dysfunction. In the context of an "acute" presentation, sepsis is the most immediate and life-threatening systemic complication. **Analysis of Incorrect Options:** * **Malignancy (A):** While chronic osteomyelitis (specifically long-standing discharging sinuses) can lead to **Marjolin’s ulcer** (Squamous Cell Carcinoma), this is a late complication occurring decades later, not a feature of the acute phase. * **Fracture (B):** Pathological fractures are more characteristic of **chronic osteomyelitis** or bone tumors where the structural integrity is severely compromised by a large sequestrum or involucrum. * **Chronicity (D):** While acute osteomyelitis can progress to chronic osteomyelitis if undertreated, "chronicity" is considered a **sequela** or a stage of the disease progression rather than an acute clinical complication like sepsis. **High-Yield Clinical Pearls for NEET-PG:** * **Most common site:** Metaphysis of long bones (due to hair-pin bends in vessels leading to sluggish blood flow). * **Most common organism:** *Staphylococcus aureus* (Overall); *Salmonella* (in Sickle Cell Anemia). * **Earliest X-ray sign:** Soft tissue swelling (10–14 days). Bone changes appear late. * **Investigation of choice:** **MRI** (most sensitive for early detection). * **Sequestrum:** Dead bone (radiodense); **Involucrum:** New bone formation (radiopaque).

Q: All of the following are true about septic arthritis, except:

Escherichia coli is the commonest causative organism.. **Explanation:** Septic arthritis is a surgical emergency characterized by the infection of a joint space. Understanding the microbiology and demographics is crucial for NEET-PG. **1. Why Option D is the correct answer (The Exception):** *Staphylococcus aureus* is the most common causative organism across almost all age groups, including children and adults. **Escherichia coli (E. coli)** is a common cause only in specific subsets, such as neonates (alongside Group B Streptococcus) or elderly patients with urinary tract infections, but it is **not** the most common organism overall. **2. Analysis of other options:** * **Option A:** Correct statement. *S. aureus* accounts for the majority of cases due to its high virulence and ability to adhere to synovial tissue. * **Option B:** Correct statement. Septic arthritis is more common in children due to the rich vascularity of the metaphysis and the presence of transphyseal vessels (in infants), which allow hematogenous spread from the bone to the joint. * **Option C:** Correct statement. In children, the infection can cross into the epiphysis or cause pressure necrosis, leading to permanent damage to the **growth plate (physis)**, resulting in limb length discrepancy or angular deformities. **Clinical Pearls for NEET-PG:** * **Most common site:** Knee joint (followed by the hip). * **Diagnosis:** Arthrocentesis is the gold standard. Synovial fluid typically shows a WBC count **>50,000/mm³** with >75% polymorphs. * **Kocher’s Criteria:** Used to differentiate septic arthritis from transient synovitis in children (Non-weight bearing, ESR >40, Fever >38.5°C, WBC >12,000). * **Special Organisms:** *Neisseria gonorrhoeae* is a common cause in sexually active young adults; *Salmonella* is classic in patients with Sickle Cell Anemia.

Q: Which of the following is NOT a cause of neuropathic joint?

Psoriasis. **Explanation:** A **Neuropathic Joint (Charcot Joint)** is a progressive, degenerative arthropathy caused by a loss of pain and proprioceptive sensation. Without these protective mechanisms, repetitive microtrauma leads to joint destruction, instability, and deformity. **Why Psoriasis is the Correct Answer:** Psoriasis is associated with **Psoriatic Arthritis**, which is an **inflammatory** seronegative spondyloarthropathy. It is characterized by synovial inflammation and bone remodeling (pitting of nails, dactylitis) but does *not* involve sensory loss or denervation. Therefore, it does not cause a neuropathic joint. **Analysis of Incorrect Options:** * **Meningomyelocele:** A common cause of neuropathic joints in **children**, typically affecting the ankles and feet due to spinal cord malformation and associated sensory deficits. * **Tabes Dorsalis (Neurosyphilis):** Historically the most common cause. It classically affects the **knee** joint due to damage to the dorsal columns of the spinal cord. * **Leprosy:** A major cause in developing countries. Peripheral nerve damage (especially the ulnar and peroneal nerves) leads to sensory loss, frequently resulting in Charcot joints of the **hands and feet**. **NEET-PG High-Yield Pearls:** 1. **Most Common Cause Today:** Diabetes Mellitus (typically affects the **Tarsal/Metatarsal** joints). 2. **Syringomyelia:** Classically affects the **Shoulder** (Upper limb). 3. **Clinical Feature:** The "6 D’s" of Charcot Joint: Distension, Density (sclerosis), Debris, Disorganization, Dislocation, and Destruction. 4. **Key Sign:** A hallmark of a neuropathic joint is a **painless** joint that appears clinically "destroyed" or severely deformed on X-ray.

Q: What is the most common organism cultured from acute osteomyelitis?

Staphylococcus aureus. ### Explanation **Correct Option: B. Staphylococcus aureus** *Staphylococcus aureus* is the most common cause of acute osteomyelitis across almost all age groups (infants, children, and adults). The pathogenesis usually involves **hematogenous spread**, where the bacteria seed the metaphysis of long bones due to its high vascularity and sluggish blood flow in the hairpin loops of the capillary beds. *S. aureus* possesses specific surface proteins (adhesins) that allow it to bind effectively to bone matrix components like collagen. **Analysis of Incorrect Options:** * **A. Neisseria gonorrhoeae:** While a common cause of **septic arthritis** in sexually active young adults, it is a rare cause of osteomyelitis. * **C. Staphylococcus epidermidis:** This is the most common organism associated with **prosthetic joint infections** and infections related to indwelling catheters or orthopedic hardware (biofilm formation), but not primary acute osteomyelitis. * **D. Streptococci:** Group B Streptococci are a significant cause in neonates, and *Streptococcus pyogenes* can cause bone infections, but they remain statistically less frequent than *S. aureus*. **High-Yield Clinical Pearls for NEET-PG:** * **Sickle Cell Disease:** While *S. aureus* is still common, **Salmonella** is a highly characteristic and frequently tested pathogen for osteomyelitis in these patients. * **IV Drug Users:** Increased incidence of **Pseudomonas aeruginosa** (often involving the vertebral column or sacroiliac joints). * **Puncture Wounds through Footwear:** Associated with **Pseudomonas** infection. * **Neonates:** Most common organisms are *S. aureus*, *Group B Streptococcus*, and *E. coli*. * **Most common site:** Metaphysis of long bones (due to the "hairpin" arrangement of vessels).

Question 1

An 18-month-old girl presents with a fever of 104	extdegree F and refusal to walk since waking up. A hip x-ray reveals subtle widening of the left hip joint space. What is the most appropriate initial management?

Accepted Answer

Surgical drainage of the hip joint

Answer

Close observation in the hospital

Answer

Administration of intravenous ceftriaxone

Answer

Administration of intravenous oxacillin

Question 2

A patient with severe arthritis suddenly becomes unable to move his arms or legs. He is admitted to the neurology floor, but his quadriplegia does not improve with time. If the quadriplegia is due to his arthritis, which of the following types of arthritis does this patient most likely have?

Accepted Answer

Rheumatoid arthritis

Answer

Ankylosing spondylitis

Answer

Gouty arthritis

Answer

Osteoarthritis

Question 3

Which of the following crystals may give rise to pseudo-neuropathic arthropathy resembling Charcot's joint?

Accepted Answer

Calcium pyrophosphate dihydrate

Answer

Monosodium urate

Answer

Hydroxyapatite

Answer

Calcium oxalate

Question 4

What is symphalangism?

Accepted Answer

Fusion of the interphalangeal joints

Answer

Reduplication of fingers

Answer

Shortening of the fingers as a result of decreased length of the phalanges

Answer

Joined fingers

Question 5

A non-healing sinus is a common clinical feature in chronic osteomyelitis. What is the most frequent cause for this presentation?

Accepted Answer

Presence of sequestrum

Answer

Resistant organisms

Answer

Retained foreign body

Answer

Intraosseous cavities

Question 6

What are the potential complications of acute osteomyelitis?

Accepted Answer

Sepsis

Answer

Malignancy

Answer

Fracture of the affected bone

Answer

Chronicity

Question 7

Wandering acetabulum is found in which condition?

Accepted Answer

Tuberculosis of the hip

Answer

Acetabular fractures

Answer

Septic arthritis of the hip

Answer

Congenital dislocation of the hip

Question 8

All of the following are true about septic arthritis, except:

Accepted Answer

Escherichia coli is the commonest causative organism.

Answer

Staphylococcus aureus is the most common causative organism.

Answer

It is common in children.

Answer

It can affect the growth plate.

Question 9

Which of the following is NOT a cause of neuropathic joint?

Accepted Answer

Psoriasis

Answer

Meningomyelocele

Answer

Tabes dorsalis

Answer

Leprosy

Question 10

What is the most common organism cultured from acute osteomyelitis?

Accepted Answer

Staphylococcus aureus

Answer

Neisseria gonorrhoeae

Answer

Staphylococcus epidermidis

Answer

Streptococci

Arthrology and Infections — MCQs

Arthrology and Infections — MCQs

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