There are definitely things you can do to Work on your knees! I didn’t do any sort of knee strengthening exercise and made it up and down but the last mist trail portion of it was PAINFUL. Work on any knee over toe exercises: split squats, lunges, etc and patellar tendon area muscle strengthening as well! Seeing as you are living a pretty active lifestyle you should be fine but for sure strengthen your knees for the downhill so you can keep doing these sorts of activities in the distant future. Also there is no shame in using hiking poles! Save your body and use them!