Welcome, Leigh!

Re knees--exercises for strengthening the muscles above and below the knee plus the use of trekking poles really helps me.

Re footwear--I have really deformed feet (fallen arches, bunions, hammertoes) and have found that using trailrunners instead of boots really helps--I can get a far better fit with better support for my feet, and trailrunners are both softer and lighter. (There are some soft and light boots, but I haven't been able to find any without Goretex liners, which turn my feet into a sauna.) Also, ditch the manufacturer's insoles and find after-market insoles that work with your feet. I would have avoided my latest problem (plantar fasciitis) if I'd switched to green Superfeet (which work really well for me, Your Mileage May Vary) a long time ago!
May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey