So, if you had a slightly unsound horse, who was off for a few strides of trot (especially uphill) then fine, would your first port of call be the vet or the physio???
Vet - especially as physios/osetos/massage people are not "meant" to practice without your vets permission - as I found out when asking for a recipt after my horse had these people out (long story!). Very fustrating as a lot wont even tell you they need vet consent before working on your horse (no one who came to mine did - wish they had would have saved me a lot of money!!)
Vet, physios arent qualified to diagnose or deal with lameness.
I think it's irresponsible ownership to get the physio instead and no good physio should agree to treat an unsound horse without the vet having seen it first