Hey All SM users.

I've got a question about the muscles for the leg. A muscle was placed on the back of the leg/thigh(biceps femoris) and for some reason when I move the leg the muscle does a weird s shape, where the lower part of the muscle pops over the bone to the front while the other stays behind the leg. This occurs only when I finalized the muscle. I have extended the control slightly below the knee joint which helped it from shooting straight out. I've tried to reproduce what it was doing (for my friend).

Any ideas?