kidney infections
"I took Cipro for a UTI.  Within 3 doses (1.5 days) I went from walking fine, to having severe pain in my left knee and having to limp.  The pain got worse.  Finally, I researched Cipro's side effects and found out that it can cause severe damage to tendons.  I stopped the medication, but the damage was already done.  A year later I had to have surgery to repair some of the damage.  Since then I have read other horror cases like mine.  Cipro seems to find a weak tendon and strike at it.  I will never take this drug again."