כְּ֭תֵפִי מִשִּׁכְמָ֣ה תִפּ֑וֹל וְ֝אֶזְרֹעִ֗י מִקָּנָ֥ה תִשָּׁבֵֽר׃
就願我的肩膀從肩胛脫落，願我的手臂從臂骨折斷。
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.
כְּ֭תֵפִי מִשִּׁכְמָ֣ה תִפּ֑וֹל וְ֝אֶזְרֹעִ֗י מִקָּנָ֥ה תִשָּׁבֵֽר׃
就願我的肩膀從肩胛脫落，願我的手臂從臂骨折斷。