extremities

Reader's Digest 12/1月合併号の記事 'Stretch Yourself' からの引用です。

Brady Peterson, 75, a retired university professor in Belton, Texas, had always been physically active, working out in a home gym and walking six to ten miles a day. Then, about four years ago, after experiencing gradually increasing stiffness and pain in his extremities, he was diagnosed with polymyalgia rheumatica, an inflammatory disease that can affect every part of the body.

"extremities" は　"extreme" から推測すると、身体の末端、手足を意味している様ですが、辞書で確認します。

・Oxford English Dictionary: extremities The hands and feet.: ‘tingling and numbness in the extremities’

・Collins Dictionary: Your extremities are the end parts of your body, especially your hands and feet.: He found that his extremities grew cold.

・Cambridge English Dictionary: the parts of the human body furthest from the heart, for example, the fingers, toes, and nose: Few women took advantage of the opportunity to report additional symptoms-breast pains, buzzing in ears, tingling of extremities and irritability were mentioned.

この意味では必ず複数形の "extremities" で使うとありました。