Originally Posted by smrobs
Truthfully? I would go ahead and have the vet out anyway to give him a good once-over. If he's biting/rubbing on his hip bones (if so, then he has got to have a super long neck), he may be hurting somewhere back there, he may have ulcers, it may be a stress habit from being at the track.
If he's laying flat for long enough periods of time to cause pressure sores on his hips, then there is something serious going on there. A lazy horse might lay out for 2-3 hours a day and they will often alternate between laying flat and laying more on their stomach with their legs curled up. Certainly not enough to cause pressure sores.
As for treatment until you can get the vet out, I would stick with some sort of triple antibiotic ointment (the +pain type couldn't hurt, just to numb a bit of the irritation from the wounds). Avoid rinsing it too often as that can promote proud flesh.
I believe proud flesh only grows on the legs where there is no muscle. I think the hips are more likely pressue sores too. Deep, deep bedding will be the most helpful until weight is gained.
I would try deep shavings covered with deep straw.