[Margaret Pilkington]

I think it may be down to the fact that when you have had knee pain for many years you walk differently....your body alignment is different. you walk in a way that minimises the pain.
Once you have had a knee replacement you may still walk in the way you did before you had the op.
My next door neighbours son has had a knee replacement recently but he still walks like he did when he had the pain and the limited movement with his old knee.
I mentioned this to him and he said that I was not the first person to tell him this.
He is consciously trying now to normalise his gait.

I cannot explain why it would only manifest itself after such a period of time though.

This theory of mine is just that,a theory...not based on anything I have experienced in my past working life.