Muscle · Shoulders

Latissimus dorsi

Musculus latissimus dorsi

The largest muscle of the back by area — a broad sheet arising from the lower spine, the sacrum, the back of the pelvis and the lower ribs, sweeping up and out to twist into a narrow tendon at the front of the upper arm bone. It pulls the arm down, in, and rotates it inward: the pull-up, the swim stroke, the push out of an armchair. What makes it clinically interesting is its reach. It is the only muscle connecting the arm directly to the pelvis, bypassing the shoulder blade altogether, so tightness here can restrict overhead reach and load the low back at the same time.