What Is The Sever Pain In My Knees With A Minimal Effusion Seen In MRI?

Hi I was diagnosed with eosinophilic granuloma when I was 19 years old after I found a depletion in my skull, It was surgically removed,I had a CT scan of the bone and they found lesions in my left femur, but didn't do anything about it. Now I am 33 years old, I have alot of pain in my knees, I did MRI for the right knee, they found minimal effusion, i wasn't diagnosed of any rheumatoid disease, and the Dr said I need rest and sleep. I am not convinced and worried about my knees, because pain doesn't go and I am wondering if it could be related to the old diagnosis of eosinophilic granuloma?