Companion Laser make the Class IV system I use. They publish a list of the conditions their therapy is indicated for, and the groups below are taken from it.
It is worth being clear about what that means. This is the manufacturer's list, not a set of promises from me. It shows the range the technology is used for across veterinary practice, which is much wider than the mobility work most of my clients first ask about.
This is an extract. Their full list is longer. I have left out the conditions that belong to other species, the procedures that are carried out by a vet rather than by me, and anything urgent enough that the right response is a phone call to your vet, not a laser appointment.