Inner knee pain when stretching

[Noel]

Hello all. I have Tom Kurz's book and video. I have been doing the suggested exercises from the book and video but I seem to be having great difficulty with a pain in my inner knee, both left and right. When I do the side split isometric stretch, I orient my feet so they are facing forward and flat. The pain starts from the inner side and runs down to half calf, same side.
Is the reason why there's pain in my inner knee when doing the side split stretch is because of wrong foot orientation or is it more of weak inner knee muscles?
Can you suggest some exercises to strengthen my inner knee muscles?

Thanks for any help.

[Thomas Kurz]

Do more horse-riding stance training and keep your knees bent when sliding into a split. See my answer to the Post subject: Knee pain and split training. It is a different problem (there a pain on the outside of the knee, here on the inside) but the solution should fit.