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Septic Arthritis

Red 2

Step 1: View clinicals

A 50 year old postmenopausal woman presents with a red, swollen left knee which is painful to touch. There was no history of fever, rash, diarrhea, uveitis, prior knee swelling, antecedent trauma, knee surgery, or risky sexual behavior. She was diagnosed with rheumatoid arthritis 2 years ago, and is on long-term low dose corticosteroid therapy.

Step 2: Order all relevant investigations


WBC 50,000/mm3 (<200) Polymorphs: >50% (<25%) Gram stain: multiple gram positive cocci noted Cultures: will be available in 3 days Crystals: negative

Full Blood Count

WBC: 9,500/ mm3 (4,000 - 10,000/mm3) N: 93%, L: 5% Hb: 12.3 g/dL (11.5 - 17.5) Platelets: 320,000/mm3 (150,000-450,000)

Blood Cultures

Gram Stain: Multiple gram positive cocci are noted Culture reports will be available in 3 days.

X ray L/Knee

There is widening of the joint space suggestive of a moderate effusion. There is no evidence of joint destruction.

Step 3: Select appropriate management

IV Antibiotics
Stop Corticosteroids
Immobilize joint
Joint drainage

Score: ★★☆