I have never heard of Shih Tzu with any problem like that.
I have had two my Buster lived to be 12 he was a overweight boy that I rescued at 6 yrs of age even though he was large for this bred he never acted like that. My 4 yr old Jordie is fine aswell, if I were you I would again go to the Dr and get some real answers start with a X-ray that would really help. Let us know what you find out please
