“My knee’s blown up — it’s just my arthritis”

A single, acutely hot, swollen, red, painful joint with inability to weight-bear is septic arthritis until proven otherwise — a joint-destroying emergency that cannot be diagnosed or excluded by phone and must NOT be managed as "just an arthritis flare" with painkillers. The risk factors here stack damningly: a recent intra-articular steroid injection (a portal of entry that raises, not lowers, concern), diabetes (immunocompromise), age and pre-existing joint disease; and systemic upset (shivery, feverish) raises sepsis concern (screen by phone with the NICE NG253 red flags; his erratic glucose matters for his diabetes but is not itself an NG253 criterion) — though septic arthritis can be present without florid fever (BSR/BHPR 2006: treat as septic arthritis on high clinical suspicion even without fever). The action is urgent same-day hospital assessment for joint aspiration (ideally before antibiotics), without advising nil by mouth at home in a man with diabetes, recognising that a crystal/OA history does not exclude infection (they coexist). The examinable hidden agenda is hospital fear driven by grief — his wife died after a hospital admission — making him minimise emergency features to stay home. Hear the fear and grief with compassion and use them to bring him to assessment, convey urgency without panic, refuse "wait it out", and confirm he goes.