About A Year Ago I Fell On My Knee. After

About a year ago I fell on my knee. After weeks of no treatment then P T and medication , they did an M R I which showed a tear. The Dr said she wasn't sure it wasn't just bruising , and arthritis (for which I had no prior problem) It has been a year and find it almost impossible to walk without a pain level of at least 15/10, and the feeling my knee will buckle. Am I just doing more damage to my knee. What sure further treatment be?