Don't stand too long
You can try to change your foot position by resting one and alternating them on a book or footstool simulating a brass rail in a bar. Just walking a few steps periodically or squating can help.
Some pelvic tilts can help as well as a simple elastic back support. Weight control, regular exercise
and not smoking
( if you do) will also help. Sometimes a local heat application can help -otc patches.