@fde11 If you have issues that affect body alignment such as the pelvis, it can affect alignment of the knees and cause pains on one side of the knee. When I get that, I know I need to adjust my pelvis with an exercise that my PT showed me. She also said that ignoring knee pain can cause wear and tear that may lead to a knee replacement later on. Prevention is a lot better than a knee replacement.

Here's a link to a somewhat complicated explanation about how alignment issues can compress nerves and mimic spine problems. Since symptoms change from being seated to standing, that is a clue you must tell your providers which would help them diagnose the issue. Those symptoms could also indicate a possible spine issue and this is important to discuss.

"How to identify and treat lumbar plexus compression syndrome (LPCS)"
Posted on March 30, 2017 by Kjetil Larsen
https://mskneurology.com/identify-treat-lumbar-plexus-compression-syndrome-lpcs/
Have you considered consulting a physical therapists for an evaluation?