I Got A Knee Injury 06/15/2015 At Work I Slipped

I got a knee injury 06/15/2015 at work i slipped while I was on a roof. My left leg went one way and the rest of me fell backwards. Ive been to 3 occupational medicine docs. I had 3 xrays 2 mri's today is 08/15/15 and I cant put no pressure on the knee, it's in extreme pain. the docs told me it was Osteoarthritis. Ive had a steroid shot last week and no relief. I am 39 years old no prior pain in that knee.But the pain is getting worse. Any suggestions?