Can you get the model "stl" from > http://www.thingiverse.com/search?q=hand+skeleton&sa and export it to "VRML V2.0" whit "FreeCAD"?

Thanks for your information

Do I need to add rotational axis to each joint by myself?

If I understand correctly, If the bones aren't separate, I think you need cut the mesh and separately manipulate each bone.

That may be of a huge workload. Thanks!