1.spasm

N-VAR A spasm is a sudden tightening of your muscles, which you cannot control.

2.knack

N-COUNT A knack is a particularly clever or skilful way of doing something successfully, especially something which most people find difficult.

3.twinge

N-COUNT A twinge is a sudden sharp pain.

4.knead

V-T If you knead a part of someone's body, you press or squeeze it with your fingers.