DiDi,
I am currently experiencing the exact same problem. In fact, it almost feels like a giant rubber band is not stretching behind my knee because some days I cannot even stretch it out straight! I have been to both the dr and a physical therapist for this. The dr feels like it's my muscles; the pt thinks it's my joints. I personally feel like it's muscles. I have tried walking more to stretch it out and that works until I sit down. I have been doing the Wedding Tape Part II and the lunges hurt but they strengthen. However, the next day, I can hardly stand! There are supposed to be great stretching exercises for this but the only ones I have found that help at all are Karen Voight's Simple Stretch. If you find out anything, please let me know!
thank you
teri