Why is my knee pain worse during the night?

Q) I have osteoarthritis in both knees, not very severely, and can still walk short distances. However, in bed at night, I tend to wake up about 4 or 5 am with considerable pain in my left knee, sufficient to make it difficult to go back to sleep. Can you explain why it should be more painful when I'm in bed? Is there anything I can do about it, apart from taking painkillers?
Susan Pomeroy, Harpenden, Hertfordshire (Winter 2010)

A) This is a common problem. There may be a number of reasons why this occurs. Night pain is often an indicator of severity and is used to assess the need for further treatment, such as an operation. From what you say, this may not apply in your case. It may be worth getting a medical ‘update’ on your condition, however. Sometimes pain is more noticeable when there's little else going on but, in that case, people usually find it difficult to get off to sleep. If you're woken up by the pain it suggests that the arthritis has reached a more advanced stage. It may help to take a drug with a long duration of action, say 12 hours, at bedtime. Some anti-inflammatory pills are formulated in this way, as are some painkillers – they're usually labelled ‘modified (or slow) release’.