Anatom3DRotator cuff
Musculotendinea rotatoria · Rotátorová manžeta
Muscles
Looks like
Four flat muscles wrapping the shoulder from the shoulder blade to the top of the arm bone.
What it does
Hold the ball in its shallow socket and turn the arm in and out.
Keeping it well
Strength work at low weights; tears are common over 50 and most do well without surgery.