Muscle · Chest

Pectoralis minor

Musculus pectoralis minor

A thin triangle hidden beneath the pectoralis major, running from the third, fourth and fifth ribs up to a hook on the front of the shoulder blade. It is small and it is disproportionately important. Because it pulls on that hook — which sits in front of and above the shoulder joint — a short pectoralis minor tips the top of the shoulder blade forward, lifts its bottom corner off the ribs, and turns the socket to face downward. That is the exact opposite of the position the arm needs in order to reach overhead. Momentum's clinical system puts it on the commonly-tight list for the upper body and names the failure it produces — scapular upward rotation failure — as the movement problem behind shoulder pain.