If only inflammation then an antibiotic will not help.
Cosequin is supposed to help with just inflammation.
I myself would only use Covenia under rare circumstances, like a semi feral cat I could not pill. http://www.catinfo.org/?link=convenia
If a UTI then best is to have Culture and Sensitivity test run to find suitable antibiotics. Clavamox and Baytril are good general antibiotics.