I started running this year. I'm 46, and I've spent most of my life with a long list of injuries — knees, ankles, hips, take your pick.
Three things made the difference.
First, run with your hips. Picture a galloping horse — knees come up high with every stride. What that does is change where your foot lands. It comes down straighter, more parallel to your hips, instead of reaching out ahead of you. Land ahead and you have to pull the ground toward you with every step. Land under your hips and you push the ground away instead. Same motion, opposite physics — one wears your joints down, the other builds them up.
Second, the shoes matter. The flatness of your feet is what leads to injury. If your feet are flatter, your ankles roll in when you land, and that pulls your knees in right along with them — stride after stride, until something gives. Buy shoes with a higher bump on the inside and it balances the curve your foot is missing, so the landing spreads evenly across your ankles, knees, and hips instead of loading one side. If you want more info go to a running store, they're pros at checking for this.
Finally, learn to run backwards. It sounds like a gimmick. It balances your whole body. Running backwards strengthens your hips and the upper part of your knees, and because you land on your toes instead of your heels, it builds out the front of your calf, a muscle forward running never touches. I've found it to be the best way to strengthen your legs and balance the power. Look at a tennis player's legs. That's what you want.