Lame horse- in or out?

[Abby&Apollo]

My 7 year old ex racer is bilaterally lame behind.
last year we had this issue and it led to us finding out he had kissing spine, and he was lame due to overcompensating from the pain.
However now the weather has gone cold he’s been running around the field every day so it’s also likely he’s just pulled something too rather than it being his back again.
if he doesn’t improve I’ll be calling the vet back out, but until then would you turn out or bring in?

 

[Red-1]

If you think was caused by the cold weather, I would have thought bringing him in would be the obvious choice?

I would also call the vet tomorrow.