Can sciatica cause knees to swell after standing or walking for awhile? or tightness behind knee? i feel the nerve behind my thigh sometimes..maybe its irritated. when i do sciatica stretches i feel some relief. knee hasnt been swollen for some time?

Are you overweight is my concern, however sciatica is used to describe the compression on the sciatic nerve that may come from abnormalities in the structures as it comes out of the spine, it may show is pain behind the thigh . The knee swelling is probably a different issue and it is best to get physical evaluation for better management.

Swelling of knees is a local knee joint phenomenon, possibly due to injury to cartilage or other internal structures, and has NO relationship to sciatica which represents a problem with the sciatic nerve. Pain is commonly experienced over the posterior thigh.

Your sciatica pain could be do to a limb length difference or pelvic rotation Piriformis syndrome