posterior border of ulna

pos·te·ri·or bor·der of ul·na

[TA] the sinuous palpable subcutaneous ridge on the posterior aspect of the ulna that extends from near the olecranon to the styloid process, demarcating the "anterior" (flexor) from "posterior" (extensor) compartments of forearm. Synonym(s): margo posterior ulnae [TA]