thank you to everyone who replied. She doesnt seem to be in any pain when she is limping,maybe because she is on a daily dose of metacam. Sometimes she just sits down as it seem to collapse,and she also sometimes freezes half way up the stairs when her legs cant propel her to the top. The left one is the worst,even though it was the right one that she started lifting up first. She seems to hold it out straight behind her,does this sound like her patella?.We have had a lot of snow here this week and she runs about in it,like any puppy would,but limping her way along. I feel like crying for her ,but my husband and family keep saying she isnt in any pain or she would be yelping.I wish I could wave a magic wand and have her legs back to normal.I have covered the wooden floor in the kitchen with rubber backed mats so she doesn't skid,and we are trying to keep her weight down,as the vet said that might help. We can't avoid stairs as we live in a town house with 3 flights of them.

Lindylou, we picked the name Ailsa,as our older cavalier is called Skye and we thought another Scottish island name would be nice. We used to see Ailsa Craig in the Firth of Clyde, from the window of my friends caravan when we went away for a few days,and thought that suited her.
Thanks once again to everyone who took the time to reply,and I will let you know how she is. I will just have to buy a big crate and anything else she needs,and I will sleep in the livingroom with her,as it has the access out to the garden ,and she wont need to go up stairs at all