Wisteria looks sick
This is a difficult one to diagnose but in this case, you want to look down instead of up. I think I see what may be galls at the base of the trunk. The galls are will look kind of like a wart at the crown of the plant. Although wisteria is a tough plant and vigorous grower, you may have what is called crown gall, which is caused by bacteria. I would recommend you take a few more photographs (especially around the base) and take them in to your county master gardener office http://extension.oregonstate.edu/mg/metro/questions
I recommend you ensure the plant gets adequate water (maybe 5-10 gallons per week during hot weather) but would avoid any additional fertilizer.
I will say with my own experience with wisteria, I had complete dieback and it has since grown back (it was ~15 years old when it died back and it's been going strong for the last five years but it hasn't bloomed yet.) I need to do some pruning on the vine to help promote that bloom, but I wanted to make sure the vine was really growing before any significant pruning during the growing season.
Good luck and thank you for posting to 'Ask an Expert'
Thank you for your help! We will follow up with our Washington County extension office with more pictures.