Overview
Septic arthritis is a joint infection that can rapidly damage cartilage and bone. It is a medical emergency requiring prompt treatment.

Causes and risk factors
Bacteria most commonly cause the infection, usually spreading through the bloodstream or from nearby infection. Risk factors include older age, immunosuppression, joint replacement, and intravenous drug use.

Symptoms
Severe joint pain, swelling, warmth, fever, and inability to move the joint.

Diagnosis
Urgent joint aspiration to analyze synovial fluid and culture is essential. Blood tests and imaging support the diagnosis.

Treatment
Immediate antibiotics and joint drainage are required. Delays can lead to permanent joint damage.

When to seek care
Any acutely swollen, painful joint with fever should be treated as an emergency.