--I imagine the lidocaine by itself would deaden the pain for at least some hours. It would be like getting a injection for dental work.

Dexamethesone is itself a very potent anti-inflammatory, and is often used in podiatric practices for foot and toe injuries. It's notoriously difficult to reduce inflammation in that area, as the blood supply is not very good--and gravity doesn't help with the circulation; moreover, we ARE constantly using/putting pressure on that part of the body.

There are a considerable number of side effects to using injections of this regularly (the Wikipedia article on it lists a lot of them), so I suspect whatever regimen the doctor decides will have to be spaced out and carefully monitored.