subtendinous bursa of the tibialis anterior muscle

sub·ten·di·nous bur·sa of the tib·i·a·lis an·ter·i·or mus·cle

(sŭb-ten'din-ŭs bŭr'să tib-ē-ā'lis an-tēr'ē-ŏr mŭs'ĕl)
The small bursa between the medial surface of the medial cuneiform bone and the tendon of the tibialis anterior.