A 50-year-old man presents with knee pain that is worse at night and often wakes him from sleep. He also reports occasional fevers and has lost weight without trying. His knee is warm and swollen on physical examination. What is your preliminary diagnosis and next steps?
These symptoms could be suggestive of a serious condition such as an infectious (septic) arthritis or malignancy. Both conditions can present with knee pain that is worse at night, along with systemic symptoms such as fevers and weight loss. Urgent diagnostic evaluation is necessary, including joint aspiration to evaluate for infection or malignancy, and blood tests including complete blood count, inflammatory markers (CRP, ESR), and cultures. If septic arthritis is confirmed, urgent surgical washout and antibiotic therapy will be required.