Acute arthritis as an unusual complication of malignancy

SUMMARY A 59‐year‐old man presented with an inability to weight‐bear due to an acute, red, hot, swollen knee joint which was subsequently found to be due to a malignant joint effusion consequent to colonic carcinoma. Treatment with radiation therapy relieved his symptoms. A review of the literature reveals that malignant joint effusion is rare and this is only the third reported case secondary to colonic carcinoma.