I WAS PERSCRIBED AND HAVE BEEN TAKING MINOCYCLINE FOR A

I WAS PERSCRIBED AND HAVE BEEN TAKING MINOCYCLINE FOR A CASE OF EXCEMA THAT STARTED IN aPRIL 2016 .1. wHY WAS THIS ANTIBODIC CHOOSEN ? Anything I read has said nothing re: excema 2 . Have been on for 2 weeks - and still 2 weeks to complete -why this length? 3. Not sure if related or not but x1 week of inc pain behind L knee, now swollen and very painful . Am barely able to walk. I am athletic and run, work out and yoga , but have not for x3 days - but knee is worse. Any relationship??