I'm wondering whether the pilates helped clear it up Aileen so that he didn't need an operation and/or that he was advised against an op in the end. I would definitely recommend pilates for the lower back -it helps strengthen the muscles and also teaches you better posture.
The thing is though that we still don't know what the problem is, but given that Andy has said it's something that might always be with him, plus the fact that playing football and golf is a no-no, at least while his tennis career is still on the go, it would tend to fit the diagnosis a physio acquaintance suggested last year, i.e. that it most likely is a lumbar degenerative disc - something which sounds pretty alarming but which is actually very common in sports where constant rotating of the back is involved. The good news is that it's easily managed and that surgery is usually only required in severe cases where mobility is regularly compromised. Also any pain from the condition can, over a long period of time, and for complex medical reasons, decrease rather than get progressively worse.