bsically my knees are knackered Dave, i'm sort of ok if i'm really careful but its silly little knocks like this that keep hurting me

was told about 12 years ago i needed replacements but the NHS dont want to know & i can't afford private!
i suppose 25 years of paying tax & national insurance along with a white face excludes me from any free treatment i thought i might be entitled to?
i just gotta be careful, they let me know what i can & can't do!