Shoulder Stiffness, Stiff Shoulders, Stiff Neck
noun
When your shoulders get a little こり, it means you've got shoulder stiffness or a stiff neck. The こり here is a nominalized version of the verb こる, which means "to become stiff," so maybe that'll help you remember this!
かたこり
You already know the reading of 肩, and this is just that with some hiragana added on!
これは肩こりが楽になるストレッチです。
This is a stretching exercise that helps relieve stiff shoulders.
肩こりをほぐす良いマッサージがあります。
There is a good massage technique to loosen stiff shoulders.
スマホゲームばっかりしてるから肩こりになるんだよ。
You're experiencing shoulder stiffness because you spend too much time playing smartphone games.