Has anyone seen studies on the best beds for large dogs - like a Border Collie - with bad hips?
Medical "science" for decades claimed that a firm bed was best for people with bad backs. Recently this was debunked and now a softER bed is recommended.
Costco sells round pet beds about 3' across that is filled with what looks like spun polypropylene or similar. Initially the bed filling is uniform and about 6" high which squashes to about an inch but it tends to go lumpy after a couple of months. It seems to me that the filling needs to be different - like a medium density plastic foam. Anyone know of such a bed? Maybe I should go to an upholsterer and have one made. Should be no more trouble than making a cushion for a big armchair. Or buy the foam slab and put it in a big pillowcase.
I found the best bed & cheapest by far is to get one of those egg crate foam toppers that you put on your bed. I buy a queen size topper twice a year split it into 4 pieces then stack 2 pieces together and fold a clean sheet or polar fleece around it for my dogs. When the sheet gets dirty take it off and wash it up like you do anything else. You can wash these foam pieces if you want but you can't agitate them or they shred. I find it just easiest to throw them out every 6 months and get the dogs new ones.

a big pillowcase. TIA RF

I went out and bought a crib mattress made out of a firm foam. They are plastic lined and fairly inexpensive ($30+ at Walmart)