Having lived with rheumatoid arthritis for 40+ years, following four hip replacements and two knee replacements I've always managed to regain a reasonable level of mobility. That is until I had to undergo spinal fusion five years ago. I really struggle to stand for more than a couple if minutes and if I set off walking I feel my core muscles are too weak to keep my upright for long. Does anyone know of or use an exercise regime other than swimming that can help me rebuild core strength. Typucally I suffer from other movement restrictions and muscle weakness which hinder me too, any ideas would be gratefully received.