It is all about the hips. Many of the lower body pain problems in running are due to weakness or inability to activate muscles in the hip complex. These hip exercises are recommended by Dr. Reed Ferber of the Running Injury Clinic at the University of Calgary. Based on his studies, he found that 6 weeks of these exercises solve 92% of runner knee pain issues. I have found that most runners will see a significant reduction in knee or IT Band pain after about 3 weeks (your mileage may vary). I am not a doctor so I recommend you see a professional (but I know most runners hate seeking professionals, or you can do these non-running exercises while waiting to get an appointment…).
Here are the recommended exercises for those who are experiencing pain, or would like to prevent pain and dysfunction (i.e. All Runners!). You can perform them while watching TV or YouTube cat videos.
If you can only do just one exercise, make it this one.