Quadriceps stretch is a very good relaxing exercise for overworked quadriceps muscles ( front of thigh muscles) and specifically for ANTERIOR KNEE PAIN ( patients with pain over front and just above of knee cap ).
This is a video graphic representation of quads stretch exercise in standing position & Prone position
Need to do this exercise with 10 secs holds in stretched position for at least 5 times in a row every morning or before & after workout to relax your strained muscles.