you want to strengthen the muscles
that support the knee joint and its ligaments/cartilage/tendons/other.
"cranking" joints that aren't strong enough to withstand the force can lead to sounds and sensations you'd rather have missed. and, speaking from experience, skiing offers myriad opportunties to crank the knee, even/especially when that's the last thing you want to happen.
conservative starters (even if you aren't "aging"
i prefer the bike as a foundation then add other exercises and activities to supplement that.