What Causes Sharp Pain In The Left Knee?

Good evening! I have had constant sharp pain in my left knee. I had previously experienced the same type pain to a little lesser degree on my right knee. I underwent 3 mos of PT and it didnt help. Then ortho decided I was a candidate for some type of injection of a filler type material in my right knee. Three shots later and it stopped hurting. They said it was only temporary 6 mos to a year relief. Now my left knee is so bad that I cannot use it to pull myself up the stairs and it hurts going down stairs. My mother has had rheumatoid arthritis since she was 30 yrs old. I am now 55. Should I go to a rheumatologist or back to the orthopedic?