The Collaborative International Dictionary of English v.0.48:

Litheness \Lithe"ness\, n.
   The quality or state of being lithe; flexibility; limberness.
   [1913 Webster]

WordNet (r) 3.0 (2006):

litheness
    n 1: the gracefulness of a person or animal that is flexible and
         supple [syn: lissomeness, litheness, suppleness]