I adopted a 11 yr old yorkie that has luxating patellar, but she has other slew of problems, but I can tell you for being 11 she runs after rabbits always outside running around and barking at vultures.. she is certainly something else, I did buy a yucca extract from 1-800-petmeds you can try it, its not expensive and I think it helps her, her leg doesn't seem to bother her here is the link
Yucca Intensive (Azmira): Supplement For Dogs and Cats - 1800PetMeds