Invisible Bone?

I’m working on a ragdoll ported from a game, but I’m having a few issues with it. I rigged the ragdoll and everything in milkshape, and I added two joints for legs that connect to the feet to make them move like legs. I didn’t assign anything to the joint because the leg is invisible, and the pelvis doesn’t move at all with the legs, but the joint doesn’t seem to export. Do I need to assign something to the joint?