Hey marcsense!

There certainly can be soft tissue restrictions due to poor mechanics and our day to day activity (ie spending too much time sitting). Tt’s worth working on any soft tissue work around the hip and trying to open up the hip and restoring any ROM available to you. You can regain this motion if it is not due to bony morphology. You can perform mobilizations such as these and do a test-retest to see if there is an improvement in your positions.

https://thereadystate.com/2011/03/episode-198-open-up-you-hips-for-better-squatting/
https://thereadystate.com/2011/06/episode-260-positional-inhibition-and-hip-external-rotation/
https://thereadystate.com/2011/02/episode-165-hip-external-rotation/

However, if there are limitations in your bone morphology mobility work cannot change that and you don’t want to push to the point of impinging or creating discomfort in the hip. So work on soft tissue limitations if there are any but again as mentioned above valgus knee can be improved by maintaining a solid arch in foot spending time working on strength and motor control around the hip.

Cheers,
Mike