Trekking Poles?

Hi Jeff! Awesome website. (I came across it while browsing Everytrail.com) My girlfriend and I recently got into hiking and it's such a breath of fresh air from the daily office grind. What are your thoughts and trekking poles and why do you use/not use them? An addition some are sold in singles others in pairs. I've seen photo's in which some hikers are using two others only one. It seems to be hit or mis. We're both in good shape though I sometimes have a little pain in my left knee (pretty minor but I'm sure it'll get worse as I age) and wondered if they're really of any benefit. (Honestly, being new to hiking I don't want to look like an idiot using a hiking pole on an pathed out trail) We got our started on the Santa Rosa Plateau (pretty easy hike with only a few hills I'm sure you're probably familiar with) but we're looking to venture into some more advanced routes. At any rate, I'd love to hear your thoughts!