The Collaborative International Dictionary of English v.0.48:

Ligamental \Lig`a*men"tal\ (l[i^]g"[.a]*m[e^]n"tal), Ligamentous
\Lig`a*men"tous\ (l[i^]g"[.a]*m[e^]n"t[u^]s), a. [Cf. F.
   ligamenteux.]
   Composing a ligament; of the nature of a ligament; binding;
   as, a strong ligamentous membrane.
   [1913 Webster]