Have not been Able to Fully Bend knees since year 2000, Is it good to keep Trying or dangerous?

I’m male early 30’s.

I used to run alot since i was a teen to my early 20’s when suddenly i got some knees sprains and tendon tear. It took a while to heal that and then i stopped dong full knee bends because i was afraid and also it started hurting more even after i healed.

So i gave up and did not do full knee bends( HEEL touching Buttock) since then. I also got my other knee injured so i didn’t do knee bends with either knee.

Well, so now I can’t even do knee bends even if I try. When the thigh and shin reach like a 10 degree angle( ZERO degrees being heel to buttock touching).. i just can’t go any further.. it hurts bad and it feels like the ligaments are gonna snap.

So my question is, should i keep trying to strenghtern my knees more and more and stretch and keep trying to achieve heel to buttock ability OR would i just hurt myself.. and i should stop trying cause it’s someting i will not be able to do ever again in my life?

I used to be able to do it before year 2000, when i used to be really athletic.

I know now i have knee injuries, but I can bend my knees down to 10 degrees so why would bending them to 0 degrees be any worse than 10 degrees is..