I have diabetes and my knee is suddenly swollen and painful. Should I worry about infection?

Why diabetes changes the picture

High blood sugar weakens the body's defence against bacteria and slows healing. Many people with diabetes also have reduced sensation, so a small skin wound or ulcer that lets bacteria in can go unnoticed. Infection may show up with less fever and fewer obvious signs, and it may be detected first as unexplained high sugar readings.

Signs that need same-day care

• One knee that has become hot, swollen and painful over hours to a couple of days
• Difficulty bending the knee or walking on it
• Fever, chills, sweats or feeling unwell, even if mild
• Blood sugars much higher than usual without another reason
• A recent injection, aspiration or operation on the knee
• A cut, skin infection or foot ulcer anywhere on the leg

Other causes of a swollen knee in diabetes

• Gout or pseudogout: crystals can cause a sudden, very painful, red knee that looks exactly like infection
• Flare of osteoarthritis
• A meniscus tear or other injury
• Bursitis in front of the kneecap, which may itself become infected

Only testing the joint fluid reliably separates infection from crystals, which is why aspiration is often needed.

Practical advice in Qatar

Check your sugar more often while the knee is swollen and keep drinking water, particularly in summer heat or while fasting; if you are fasting and become unwell, speak with your doctor about how to manage medication, and you can discuss religious questions with a scholar. Do not take leftover antibiotics. At Aman Hospital in Doha, Dr. Gelber can assess a swollen knee, arrange aspiration and tests, and work with your diabetes doctor. If you are unwell or the knee is worsening quickly, go to emergency care.