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Patient Case: Infectious Arthritis

Patient Case: Infectious Arthritis

Discussion

A 29-year-old male presents to a local clinic with a three-day history of severe pain, swelling, and redness in his right knee. He reports fever, chills, and difficulty walking due to the pain. He denies any history of trauma but recalls a recent episode of urethral discharge and burning sensation while urinating two weeks ago, which resolved without treatment.

On examination, the right knee is swollen, warm, and tender with a limited range of motion. His temperature is 38.5°C. Laboratory tests show an elevated white blood cell count and high inflammatory markers (ESR and CRP). Joint aspiration yields purulent fluid, and Gram stain reveals intracellular gram-negative diplococci.

A diagnosis of septic arthritis, likely due to Neisseria gonorrhoeae, is made. The patient is admitted for intravenous antibiotics and joint drainage to prevent joint destruction and systemic complications. He is also counseled on sexually transmitted infections and referred for further evaluation

Questions
1. What is the most likely cause of this patient’s arthritis?

a) Rheumatoid arthritis

b) Gout

c) Septic arthritis due to Neisseria gonorrhoeae

d) Osteoarthritis

2. Which of the following findings best supports the diagnosis of septic arthritis?

a) Chronic joint pain with morning stiffness

b) Purulent joint fluid with intracellular gram-negative diplococci

c) Normal white blood cell count and inflammatory markers

d) Bilateral joint involvement without fever

3. What is the most appropriate initial treatment for this patient?

a) Nonsteroidal anti-inflammatory drugs (NSAIDs)

b) High-dose corticosteroids

c) Intravenous antibiotics and joint drainage

d) Physical therapy alone

4. What is the most important complication if this condition is left untreated?

a) Permanent joint destruction

b) Mild, self-limiting joint pain

c) Recurrent gout attacks

d) Asymptomatic joint stiffness

Reveal answers

Answers

1. c) Septic arthritis due to Neisseria gonorrhoeae

The patient’s history of recent urethritis, acute monoarticular arthritis, and purulent joint aspirate with gram-negative diplococci strongly suggests gonococcal septic arthritis. Other causes like rheumatoid arthritis and osteoarthritis are unlikely given the acute presentation.

2. b) Purulent joint fluid with intracellular gram-negative diplococci

The presence of pus in the joint fluid and gram-negative diplococci confirms septic arthritis, a medical emergency requiring urgent treatment. Other inflammatory arthritis types usually lack purulent fluid.

3. c) Intravenous antibiotics and joint drainage

Prompt treatment with IV antibiotics (effective against N. gonorrhoeae) and joint drainage is critical to prevent joint destruction and systemic spread of infection. NSAIDs and corticosteroids do not treat the infection.

4. a) Permanent joint destruction

If left untreated, septic arthritis can cause severe joint damage, leading to permanent disability. Early intervention is crucial to prevent complications such as osteomyelitis or sepsis.