RBS charge only £15, but the exchange rate isn't as good. That's where the bank makes it's large cut, leaving you thinking you're getting a bargain when you're not.
It's all fine talking about diet etc, etc, but she's the one in pain.
We went through the injections. In the end they just speed up the break down of the knee by masking the problem, and allowing the joint to wear faster.
In the end it's your partner's pain, you should really do what she wants or requires.
My wife has had both knees replaced. She has minimal pain now (right knee only), which could yet improve because it's not yet a year since it was done.
After she had her first knee replaced, they asked about her second knee, and she had no hesitation at all. Which tells you all you need to know.