Army medical discharge?

I have been in the army for almost a year now...I had a motorcycle wreck a few years ago...My knee at the pavement at about 60 mph...I healed from my injuries...Now my knee is starting to give me problems espically after long periods of standing and in cold weather...its getting worse and worse. espically after PT...Its a coming and going pain, but now its coming more frequently. I have had x rays and MRI's done but they don't see anything wrong. it never broke. Could there really be something wrong with my knee..Would i be able to get a medical discharge for it.