Septic arthritis Flashcards
What is septic arthritis?
Septic arthritis is an infection in a joint that can rapidly destroy the joint and cause systemic illness. It is a medical emergency with a mortality rate around 10%.
What are the common causes of septic arthritis?
- Staphylococcus aureus (most common)
- Neisseria gonorrhoeae (gonococcus) in sexually active individuals
- Group A Streptococcus (e.g., Streptococcus pyogenes)
- Haemophilus influenzae
- Escherichia coli (E. coli)
What is a significant risk factor for septic arthritis in prosthetic joints?
Septic arthritis in prosthetic joints occurs in about 1% of joint replacements and is more likely in revision surgery than in the initial joint replacement.
What are the typical symptoms of septic arthritis?
- Rapid onset of hot, red, swollen, and painful joint
- Stiffness and reduced range of motion
- Systemic symptoms such as fever, lethargy, and signs of sepsis
What is the most common joint affected by septic arthritis?
Septic arthritis most commonly affects a single joint, often the knee.
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What should be considered in a young patient with a single acutely swollen joint?
Gonococcal septic arthritis should be considered in a sexually active individual. Gram stain typically reveals gram-negative diplococci.
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What are some differential diagnoses for a single swollen joint?
- Gout (joint fluid shows urate crystals)
- Pseudogout (joint fluid shows calcium pyrophosphate crystals)
- Reactive arthritis (triggered by urethritis or gastroenteritis)
- Haemarthrosis (bleeding into the joint, often post-trauma)
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What is the first step in managing septic arthritis?
Joint aspiration is performed before starting antibiotics to examine the joint fluid for signs of infection, crystals, or blood. The sample is sent for gram staining, culture, and antibiotic sensitivity testing.
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What are the typical empirical IV antibiotics used for septic arthritis?
- Flucloxacillin (first-line)
- Clindamycin (for penicillin allergies)
- Vancomycin (if MRSA is suspected)
- Ceftriaxone (for Neisseria gonorrhoeae)
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How long should antibiotics be continued in septic arthritis?
Antibiotics are usually continued for 4-6 weeks. This typically starts with IV antibiotics and then switches to oral antibiotics once the patient is improving.
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What can happen if septic arthritis is delayed in its treatment?
Delayed treatment can result in significant joint damage, systemic illness, and potentially death due to sepsis.
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What is a critical tip when evaluating a young patient with a swollen joint?
In a young patient, gonococcal septic arthritis should always be considered, particularly in sexually active individuals, until proven otherwise.
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