I was dignosed with a rare knee disease this afternoon by my dr. i would like to know if its hereditary?

Ive had leg pain since i was a little girl, it got worse when i got older. when i was 19 the dr i seen said i had arthritis then said she wasnt gunna see me anymore bc i was 2 young and didnt think i needed the medication right now. it got worse over the years and im 23 now. i just started seeing a new dr and she has done an x ray and a mri on me. the results came back a few days later on the mri and they said it was negitive. i went back 2 weeks later for a check up and she proceded to tell me that i have a rare disese in my knees that cause fat cells 2 grow under my knee cap and it has made both my knee caps come off and slid arround and it also causes inflamation and pinching nerves. what i would like to know if anyone has heard of this is my son is 5 and last year he started having the same problems i did when i was 4. is this desiese hereditary? because hes showing alot of the sighns and symptoms that i did wheni was that young. and i dont want him to have to go threw what i do now at 23 years old. i may possible have to have surgery on both my knees and i would like to know also if it is hereditary and he does have it is, is there anyway he woulnt have to have surgery to get rid of his if its caught in time