I have a female cat (almost 2 years old) who was fixed when she was about 4
months old.

She seems normal in every way except often when she lies down on the carpet
to relax, she'll sit with her rear slightly up in the air.
In other words, instead of her rear leg lying on its side (parallel to the
ground), she'll have her 2 back feet against the ground.

She runs, jumps, and climbs normally. Doesn't have a limp either and doesn't
seem to be sore if I touch either rear leg.

Any ideas?  Is this just something some cats do?

Thanks in advance.