Anatomical structures to provide passive motility of peripheral nerve trunks and fascicles.

It is well known that tendons have to be able to move if the muscle contracts. It is still not generally known that any structure in the body has to be able to move passively against other structures. This is especially important for the movement of limbs. In a monoaxial joint like the humero-ulnar joint only structures in the plane of the joint axis remain fixed. Structures in a certain distance to the flexion or to the extension side have to be able to move against other structures in different levels. The amount of passive motion is dependent on the distance to the plane of the joint axis. Tissues which provide a frictionless passive motion are discussed.