i'd echo other suggestions to focus on the knee pain and what the cause of that is. trekking poles can alleviate some of that, especially on downhills, but getting to the bottom of it is the best. i've intermittently had some kind of IT Band (or otherwise related issue) that turns into patella pulling and knee pain on the outside of the knee. especially with long days and lots of miles, or road walking, or tough sections. that can be zero pain going on flat or uphill, and mild to excruciating pain on steep downhills. a knee brace, esp. with a patella cutout, helps that, as do trekking poles to take some of the jarring out. but the main issue is conditioning, stretching, etc.
that said, i'd NEVER do a hike longer than a day or two without poles. there are just too many reasons for me. downhill support, nice pacing on flat ground, critical to drag me up long uphill sections, stability to reduce possiblity of injury, stream and snow crossings, tarp or tarptent support, etc.