כְּ֭תֵפִי מִשִּׁכְמָ֣ה תִפּ֑וֹל וְ֝אֶזְרֹעִ֗י מִקָּנָ֥ה תִשָּׁבֵֽר׃
Тогда пусть мое плечо упадет с лопатки, И рука моя будет оторвана от кости.
Rashi
from its bone That is the upper bone, which is round as a reed (קנה), and because it is round as a reed, it is called so.