flexes or extends the legs.
Across her knees she flexes a large saw with one hand, while in the other she holds a violin bow.
Do not use appliances with worn or damaged flexes.
With the knee extension, the hip joint is fixed and the knee flexes and extends with the foot freely rotating.
For example the flexion of the fingers by long flexors also flexes the wrists: this is opposed by wrist extensors.