Do a search on these - there has been a lot of discussions on the merits of these. I would def. recommend them (although I have the sprenger ordinary ones not the bow balance) as would lots of other users here. Def think they are worth the money.
I do not have them but I have been looking into them and the majority of reviews have been positive ones, you can get cheaper versions of them for around £20 on ebay. I would recommend trying them first and if you find you like them and they do alleviate some of the pain then perhaps invest in some 'proper' ones.
the sprenger normal ones are just as good as the BB ones imho. i have both, and they really do make a difference to dodgy joints.
fwiw if you know anyone in Germany, get them to send a pair over, they're 1/2 the price there.
I have the normal sprengers, and they are brilliant. I can tell how they help, when jumping off. I land and my feet don't hurt. With normal stirrups, my feet would 'scream' with a crampy sort of pain. Also, they stay put on my feet.
I have them and love them. (they were throw in with my saddle as I was umming and ahhing about it) Mum has the normal and wouldnt ride in anything else (shes arthritus in her ankle). So think either are good. Although I prob wouldnt have spent the extra money if Id had to but wouldnt give them back now.