In reply to Os_878:
I haven't heard of this before, I'd still guess yoga will be beneficial but you might also need something a lot more specific.
Did you check with a doctor (instead of just a physio)? There might be something underlying the instability you need to address? (e.g. injury or other, I know surgery etc is the last resort but might be worth at least finding out what is going on exactly if you haven't already)
Post edited at 16:57