I was put on Levaquin for UTI about 8 years ago at the age of 41. I finished the medication, but started thinking I was getting rhumetoid arthritis (which does run in the family). I had a terrible time bending my knees and using a toilet -- that little bit of bend was really hard. Going up and down stairs was also problematic. I finally checked out the side effects of this drug and joint pain is one of them. My knees got back to normal about 6 weeks AFTER I finished the medication. Hopefully your friend will be better within 4-6 weeks.