kiṣru - joint of the human or animal body
(CAD k 436, AHw 488)
The first meaning quoted in both sources is ‘knot’.
PS
*ki/uṯ̣r- - joint (of the ribs, fingers, etc.)
(SED I No. 155)
Though reconstructed as an anatomic term on the PS level, the present root is likely related to, or rather derived from, Sem. *k(ʷ)ṯ̣r ‘to bind, knot, fix’