I am 10 days post op on a right hip resurface.  My pain has been manageable and I have been
weight bearing from day one.

I am having a problem straightening my right knee without forcing the issue.  My in home physical therapist has given me instructions to continually try to straighten the leg at the knee when walking and when sitting but it leads to knee soreness and pain.

Has anyone else experienced stiffness and soreness in the knee below the resurfaced hip
and how long did it last?

I'm 5 weeks post op R BHR.  I have not experienced to much stiffness in my knee. Mostly stiff in the muscles around my hip when not moving around much.  I do get pain in my knee and muscles just above my knee when I am very active or pushing myself more then usual.  It is worse at night while trying to sleep, just an uncomfortable ache.  Good Luck, and continue to progress, Tom