The Collaborative International Dictionary of English v.0.48:

Genu \Ge"nu\, n.; pl. Genua. [L., the knee.] (Anat.)
   (a) The knee.
   (b) The kneelike bend, in the anterior part of the callosum
       of the brain.
       [1913 Webster]

WordNet (r) 3.0 (2006):

genu
    n 1: hinge joint in the human leg connecting the tibia and
         fibula with the femur and protected in front by the patella
         [syn: knee, knee joint, human knee, articulatio
         genus, genu]