Unknown Knee Injury - Back Of knee, possible connections to Hamstrings

Hey everyone, im so glad i finally found this site. Now for years i have been un-able to find a cause for my knee pain. It is in both knees, and im confident that it originates from the back of the knee.

I have had this problem for about 3 years at least i would say, i am 19 years old now and it has been bothering me much more in the last year or so and i can't do anything unless i get the right medical help.

I have been to rheumatology, physiotherapy, but they don't seem to know what the problem is. The pain at the back of my knee hurts everyday, walking up stairs and cycling will cause my knee cap to hurt and the front of the knee, if i were to do a deep squat then the tendons at the back of my knee will literally hurt so bad. The physiotherapist last time i saw her months ago seemed to think that the hamstring tendons in my knees were tight - my right one more so than the left, as at the time i couldn't fully extend/straighten it without incredible pain.

It's been months now and i can straighten that knee, but it still hurts, however i didn't want that pain to be taken over because the pain im referring to has been in both knees for some time now. I just don't know what to do anymore, i would love to be able to give the doctors some suggestions on what to do as this is going on forever. A physical exam and/or palpation could be a good idea, i have suggested a physical exam and they only looked at one knee and touched it for maybe a few seconds.

Today i have read up on the Popliteal tendon, and it's insertion and deep squatting relevance seems to have a good connection, however, when reading about the condition, i don't think it's tendonitis as Ive had this for years.

Just not sure where to go with it, no direct trauma or anything, it's just kind of come out of the blue, i can provide a ton of additional information if need be, but i would hope to get some replies so i didn't want to make this a mountain of text.

Really hoping for suggestions guys, thanks!