I'm 49 and have just gone on the waiting list for a TKR after nursing mine along for a long, long time. First op was at 18 following a ski-ing injury at 16, 2nd at 20 when I was told I would need a new knee in 10-12 years time (ha!), last arthroscopy about 5 years ago. My knee was bone on bone at that point, but they wanted to put off the knee replacement for as long as possible due to my age. At the time I agreed, as it was totally liveable with. The left knee was also x-rayed 5 years ago, and my consultant said there was little to chose between the two, and that the arthritis was hereditary.
Right knee went from bearable to screaming agony pretty much overnight about a month and a half ago. I knew I was getting closer to needing surgery, but the speed that it went at completely shocked me, and I'm still reeling to be honest. Have gone from managing with just the odd paracetamol and ibuprofen as and when needed, rarely full dosage, to max dose cocodemol and naproxin, which just about allows me to function. I'm constantly limping, use a stick to help me walk, and can't walk far at all. Stairs are a problem, and I live in a 2 storey house with only one bathroom. Luckily there is a lift at work. I've also wrenched my shoulders from having to push myself up out of chairs so that they are horribly painful all the time, too. I love the thing someone else said - I'm too young to feel so old - that really does sum it up!
My doctors and new consultant have been pretty amazing - I've had no arguments at all about getting referred back into the system (I signed myself out after the last op), and my consultant was very supportive about making the decision. I get the impression that they are all quite surprised that I've lasted this long. He did say that his two concerns were my age and my weight (been piling on weight since losing mobility, plus I tend to comfort eat and was overweight anyway - BMI now 32). Clearly I can't do anything about my age, but I do need to work on the weight issue... After I came out of the consultant meeting just over a week ago, I surprised myself by falling apart a little. I thought I really wanted this TKR, and then I realised that of course I don't, no one wants it. I need it, but I don't want it - what I want is a knee that works, and doesn't hurt all the time *sigh*
I don't regret having put it off as long as I have, but if I could have the surgery tomorrow I would. There's no doubt that the time has come as it is stopping me from doing all the things I love (except eating, which doesn't help!), and the pain is just unbearable at times. I suspect that the left knee will need sorting at some point in the not too distant future, but we'll cross that bridge as and when (and keep fingers crossed that there is still an NHS here in the UK to pay for it!).
It sucks to have to deal with this when you are younger, but as others have said, arthritis is no respecter of age. If it needs doing it needs doing, and the only person who can make that decision is you. Once you have decided, you may have to push to get it, as you'll have the age thing thrown back at you again and again ad nauseum. Good luck!