Are you a runner? Are you out there, on the road, putting feet to pavement day after day? If so, there's a good chance that you're no stranger to a little knee pain every now and again.
To help prevent this very common issue runners face, the American Academy of Orthopaedic Surgeons offers the following suggestions on their website:
Stay in shape. Good general conditioning is important to controlling and preventing patellofemoral pain. If you're too heavy, you may need to lose weight to avoid over-stressing your knees.
Stretch. Before running or any other exercise, first do a 5-minute warm up, followed by stretching exercises. Stretching, particularly in the face down position (prone), will help keep the supporting structures around the front of the knee flexible and less likely to be irritated with exercise. For example, when lying prone, grab the ankle of the affected leg with one hand, and gently stretch the front of the knee. Stretch before and after exercise.
Increase training gradually. Avoid sudden changes in the intensity of exercise. Increase force or duration of activities gradually.
Use proper running gear. Use running shoes with good shock absorption and quality construction. Be sure that shoes fit properly and are in good condition. If you have flat feet, you may need shoe inserts.
Use proper running form. Lean forward and keep your knees bent. Also, try to run on a clear, smooth, resilient, even, and reasonably soft surface. Never run straight down a steep hill. Walk down it, or run in a zigzag pattern. 
