Examkin

Question

Difficulty: MediumRheumatology and Immunology

A 72-year-old male is brought to the emergency department experiencing severe, progressive right knee pain and swelling that commenced roughly 12 hours prior. His medical background is significant for hypertension, diet-controlled type 2 diabetes mellitus, and osteoarthritis. Four days ago, he underwent an uncomplicated laparoscopic cholecystectomy and was discharged home the following day. His current temperature is 38.4°C (101.1°F), blood pressure is 135/85 mm Hg, and pulse is 98/min. Physical examination of the right lower extremity demonstrates a visibly swollen, markedly warm, and erythematous knee. The patient shouts in pain with even minimal passive range of motion. Plain radiography of the affected joint reveals medial joint space narrowing, subchondral sclerosis, and a distinct linear calcification within the articular cartilage. Which of the following is the most appropriate next step in management?

  1. Arthrocentesis of the right kneeAnswer
  2. B
    Intravenous administration of vancomycin and ceftriaxone
  3. C
    Intra-articular injection of triamcinolone
  4. D
    Initiation of oral indomethacin and colchicine
  5. E
    Measurement of serum uric acid level

Answer

Arthrocentesis of the right knee
The correct next step in management for a patient with a new-onset, acutely swollen, painful, and warm joint accompanied by fever is diagnostic arthrocentesis. Although this patient's radiograph demonstrates chondrocalcinosis (linear calcification of the articular cartilage), which is highly indicative of calcium pyrophosphate deposition (CPPD) disease (pseudogout), an acute pseudogout flare cannot be reliably distinguished from septic arthritis on clinical grounds alone. Both conditions can present with severe monoarticular pain, erythema, swelling, and systemic fever, and both can be triggered by recent physiological stressors such as surgery. Because septic arthritis is a medical emergency that can cause irreversible cartilage destruction within 24 to 48 hours, synovial fluid must be aspirated and analyzed (for cell count, Gram stain, and culture) before any targeted or empiric therapy is initiated. If synovial fluid analysis reveals positively birefringent rhomboid crystals and negative cultures, the diagnosis of pseudogout is confirmed and appropriate anti-inflammatory therapy can be started.

Step-by-Step Solution

1
Identify the primary clinical problem and vital sign abnormalities.
The patient has an acute, warm, swollen, and severely painful monoarticular arthritis accompanied by a new postoperative fever (38.4°C).
Recognizing the constellation of acute joint inflammation with systemic fever is critical for triaging the urgency of the condition.
2
Analyze the provided diagnostic data (radiograph) in the clinical context.
The radiograph demonstrates chondrocalcinosis, a hallmark of calcium pyrophosphate deposition (CPPD) disease, which can cause acute pseudogout flares often triggered by surgery or medical illness.
While imaging points to a crystalline etiology, imaging alone cannot rule out a concurrent or alternative infectious process.
3
Determine the most critical condition to exclude and the test required to do so.
Septic arthritis is a joint-destroying emergency that can mimic pseudogout perfectly. Arthrocentesis with synovial fluid analysis (cell count, Gram stain, and culture) is mandatory before initiating any treatment.
Missing a septic joint leads to rapid cartilage destruction and sepsis. Therefore, fluid aspiration is always the definitive next step.

Key Concept

In any patient presenting with an acute, warm, swollen joint and fever, septic arthritis must be definitively excluded via arthrocentesis and synovial fluid analysis, even if there is radiographic evidence suggesting a crystal arthropathy such as pseudogout.
Rate this question

Topics

Rheumatology and Immunology

More questions from this topic