Hi Loz,
Sorry to head about your knee problems, and I know what you mean, 2 years ago (age 42) I had my right knee replaced after about 18 months of steroid/anaesthetic injections, and them draining the fluid off the joint. Since the bionic knee went in it's been wonderful. I also know what you mean about the weight issues, i piled loads of weight on while I was on steroids to try and calm down Arthur, and with the limited mobility due to the knee. It's certainly not easy, and I hope you're able to get the knee sorted soon.
It's quite common to get pain in the other knee/hips as you alter the way you walk to try and make things more bearable, and this upsets them.
I'm not sure if this might help, but I've been doing quite well with keeping an eye on calories using
www.myfitnesspal.com although it's US based site, most UK brands and supermarket food is in it's database. It's also free to use too which is a bonus.
Hope you soon can get your knee sorted Loz, it really makes a huge difference with a bionic one :)
Jo. x
2012 Fundraising for the National Rheumatoid Arthritis Society (NRAS)
http://uk.virginmoneygiving.com/RoboJo