What can i do about knee stiffness in teenagers?

Stretch: Knee stiffness in teenagers if not associated with redness and swelling is typically related to tight hamstrings, quads, and calf muscles. Teenagers are still in their growth phase. Bones grow faster than muscles and tendons so it is not unusual for these to become tight as teenagers become taller. A good stretching program can be very helpful. Remember stretching needs to be done daily.