The step up is probably self explanatory. Get a box, or one of those aerobic class steps. Start with both feet on the ground and step onto the box then back down, always facing toward the box. I like to do alternating R leg lead, L leg lead, so you have to switch at the bottom.
The step down begins on the box/step facing out or away from the step. You will step down just till your toe touches the ground then back up onto the box, so your weight is always supported by the same leg. It's kind of a single leg squat, but different. The key is to try to do it toward a mirror so you can monitor your hips and knee. Be sure to keep your hips level, don't let the hip kick out to one side. Also watch your knee and don't let it bow in or out which will be the tendency to try to balance. This is a slow controlled movement. Thus I like to do 10 on the R leg then 10 on the L. It is tricky so feel free to start on a lower step.
You could do single leg squats using a Smith rack and could even use a Bosu ball or some other stability device since the Smith rack will add some stability. Its a similar movement, but I like the step down better.
The point in the step up, step down, and quad extension are to work on your quad balance and hip stability, which will contribute to your quad balance. The quads fire internally to externally from full flexion to full extension. "Runners Knee" is usually caused by a tracking issue around the patella due to an imbalance. Usually it is seen in the patellar tendon but you should be able to feel if it is on the inside our outside of the patella. That will give a good indication of where the imbalance is and maybe where to focus rehab, but is best to work the full range bilaterally. However, that brings us back to where is the cause? Do you pronate, supinate, have you ever had injuries anywhere along the line, hip, knee, ankle, foot? Are your hamstrings or hip flexors weak? Those are all things to look at and area all translated into your running stride and form. The strengthening could fix it, or it could just put a patch on it. But, it should help.
Jimmy
Jimmy Archer
Pro Triathlete/Coach/Freelance Writer
http://www.jimmyarcher.com http://www.dirttri.com