My knee makes a loud crunching noise when hiking uphill; minor achyness above the knee after a long hike. Pretty hard fall 3-4 years ago. What's up?

Patellofemoral pain. Sounds like patellofemoral pain syndrome. You could try nsaids, quadriceps (vmo) strengthening with terminal knee extension exercises and hamstring stretching.
Chondromalacia. Most likely you have chondromalacia which is a wearing of the back of your kneecap. It could have been from your fall. Try nsaids and maybe a joint supplement. If no improvement get it checked out.