anyone have any similar experience, ive recently taught a class where a client literally could not do the clam exercise. instead of the muscles firing up to lift the leg a pain shot directly to her knee as she laid in fetal position ...

Hello Heidi
I haven't had experience of a client like that, however you mention the fetal position. If this lady was working in extreme flexion at the hip, then maybe there was too much tension through her the back line of her legs and lower back for some reason. You could try modifying so she is hardly flexed at all. I like to teach clam with a really open angle at the hip, almost like lying on your side fully stretched out in a long line, then just bending at the knees to take the feet behind you, on an angle of between 45 and 90 degrees from the long line of the body. You can have a little flexion at the hip if necessary for stability but as little as possible. Encourage client to squeeze their heels together before opening the knee, it really aids the correct firing pattern.