Bad knees

I would say I’m pretty healthy for someone in their early 30s. I strength train (squat/deadlift PRs are greater than my body weight) and my cardio is fine (averaging 17-18 mi/week running, walking, etc).

However, MY KNEES. Oof. I want to do a trip where the first day is around 9 miles and over 2000 ft elevation with a backpack ~40 lbs. I did it once before but my knees/shins were screaming by mile 6. I honestly expected the altitude to get to me before my knees did.

I guess if I take advil I can survive, but I’m wondering if anyone has any helpful tips to improve this? From braces to exercises to… well, anything that has worked from your personal experience.

TIA.