Hi there,
Yin Qiao (San?) doesn't lock in the thief per se, since it does not contain Huang Qi (when formulated properly). It expels Wind Heat. So it is not contraindicated, although it may not work.
One of my personal favourites for immune polyarthropathy if there is overt joint swelling is Yi Yi Ren Tang. I augment it with Qing Hao (Artemisia) to give a decent acute anti-inflammatory effect. You can further enhance the formula in this way by adding Qin Pi (Fraxinus) and Tu Fu Ling (Smilax). If the dog comes across as having a Wind Heat invasion, I'd opt for this version of YYRT if your idea of Yin Qiao San does not pan out
Steve