Rheumatology
CASE 15: PAINFUL KNEE
History
A 35-year-old man is seen in the emergency department because he has developed a
painful, swollen right knee. This has occurred rapidly over the past 36 h. There is no his-
tory of trauma to the knee or previous joint problems. He feels generally unwell and has
also noticed his eyes are sore. He has had no significant previous medical illnesses. He is
married with two children. He is a non-smoker and drinks about 15 units of alcohol per
week. He is a businessman and returned 3 weeks ago from a business trip to Thailand.
Examination
His temperature is 38.0°C. Both eyes appear red. There is a brown macular rash on his
palms and soles. Examination of cardiovascular, respiratory, abdominal and neurological
systems is normal. His right knee is swollen, hot and tender with limitation in flexion. No
other joint appears to be affected.
NormalHaemoglobin 13.8 g/dL 13.3–17.7 g/dL
Mean corpuscular volume (MCV) 87 fL 80–99 fL
White cell count 13.6% 109 /L 3.9–10.6% 109 /L
Platelets 345 % 109 /L 150–440% 109 /L
Erythrocyte sedimentation rate (ESR) 64 mm/h !10 mm/h
Sodium 139 mmol/L 135–145 mmol/L
Potassium 4.1 mmol/L 3.5–5.0 mmol/L
Urea 5.2 mmol/L 2.5–6.7 mmol/L
Creatinine 94 &mol/L 70–120&mol/LUrinalysis: no protein; no blood; no glucose
Blood cultures: negative
X-ray of the knee: soft-tissue swelling around jointINVESTIGATIONS
Questions
- What is the diagnosis and what are the major differential diagnoses?
- How would you investigate and manage this patient?