Runners knee is a layman term for Patellofemoral pain syndrome. It is a condition where structures around the knee are injured due to running or activities which involves running. There are several structures around the knee which are prone to have injuries or can get irritated due to running.
It may be due to overuse of quadriceps, tightness in the IT band, malalignment of the knee, tightness in the hamstrings, wrong tracking of knee cap etc.
It can cause pain in the Knee (front or sides), limping while walking, sometimes swelling, difficulty negotiating stairs, clicking or rubbing or grating sound of knee cap.
A physiotherapist can perform specific test to confirm this condition and can help you to manage the pain through electrotherapy and well to heal the tissues faster. You may have to reduce or stop the running activity until it gets better because it slows down the recovery process and makes it worst. A physiotherapist determines what is the source of the problem and helps to manage it by using physiotherapy techniques and providing you education and home exercise program to speed up the recovery.