Take it slow and don’t rush, g0 slow and get quality mobilization in

Dont try to fix everything in a day, take about 10 to 15 minutes EVERYDAY to chip away at it

Don’t sit to long because as you said it hurts to much

Maybe look into buying a voodoo floss band or use a cut bike tube for your hip mobility and knee

Maybe include a couple miles of walking a week to keep mobility if you can

Look into decompressing or getting your spine adjusted. 

The hardest part but try and find the root cause of your pains 

Every injury is connected your back hurt your hips and your hips dont help your knees either. The point is just to know that whatever started first is contributing to the pain in the knee, hip, whatever