staying healthy

I love this return to hiking, and just getting out in the woods...
My main concern right now though is staying healthy. While the hike UP Mt Si yesterday exercised our thighs and calves, coming down was entirely different. You'd think it would be easier, and faster, going down. But the grade is so steep in places, and with the many switch backs, the calves and thighs pain is replaced by knee pain. My left knee in particular has worried me lately, and yesterday had me making some fancy moves at times. I think this might be the thing that finally gets me into a Gym. Pushing 65, I get to go to the local Community Center here and work out "free" on certain days, and I'm even considering a splurge on a "personal trainer" for some advice.
Hike on!