In Cincinnnati the local FM station has a fit program hosted by a local woman who ran in Olympics. She often has discussions by local ortho on knee problems. Recently one said the best thing to strengthen the muscles around the knee cap were leg lifts. Just lay on the floor, tighten the quad, raise the leg, hold, make sure the quad is tight and lower.
My PT taught me these and I have been doing them for years. I started with 2 sets of 20 reps then progessed to 2 sets of 30 reps 3x per week.
And I don't run!