Poor doggie... a torn ACL is no fun. My
English Mastiff (Condi) tore BOTH of hers when she was a puppy, and I had to have 2 separate surgeries to have them repaired. 2 TPLO's (tibial plateau leveling osteotomy), as you can imagine, do not come cheap, but it so improved her quality of life, I think it was $7500 well spent.
Prior to her TPLO's, our local vet had her on a combination of Zubrin and Tramadol. While on the medications, all of her symptoms seemed to disappear.