Hi there, homeopathics are very effective on animals, there are a few for pain.
The first that come to mind is arnica, and phos ferrous — this one is more for reducing inflammation, and known as an active ingredient is thought to be an excellent Mineral for redness, throbbing, and inflammation, and can also relieve headaches and fever. When my dog was in a lot of pain due to a lactating patella — I crushed the homeopathics and dissolved them in some water in a shot glass and with a syringe gave it directly to my pup. Some people just place the homeopathics right in the water, but my dog was in so much pain she wasn't drinking or eating unless I placed the food to her under her nose since she was lame. Also, have you ever considered putting your dog on a raw food diet? This is soft food and it's done changed my dog entirely. My second dog was diagnosed with liver failure and the vet told me my only option was to put him down, I took him home and changed his diet to raw food, that was 3 years ago and he is still alive.