Lower back muscles

Lower back muscles that attach to the front of the lumbar vertebrae (and sacrum)

Lower back muscles that attach directly to the front of the lumbar spine include the psoas, quadratus lumborum and the respiratory diaphragm.

Psoas

Psoas crosses the front of the hip bone to attach to the femur.

Quadratus Lumborum

Quadratus lumborum attaches to the lumbar vertebrae from the hip bone and also from the lowest pair of ribs.

Respiratory Diaphragm

The diaphragm attaches to the lumbar vertebrae from above.

Piriformis

Note, if we include or think of the sacrum and coccyx as an extension of the lumbar spine, then we can also include the piriformis in this list.

Piriformis attaches to the front surface of the sacrum. It passes forwards and downwards through the greater sciatic notch at the back of the hip bone. From there it attaches to the femur.

Lower back muscles that attach to the back of the lumbar vertebrae (and sacrum)

Lower back muscles that attach directly to the back of the lumbar vertebrae includes the multifidus, the iliocostalis lumborum pars lumborum, the longissimus thoracis pars lumborum, the serratus posterior inferior and the latissimus dorsai.

Lumbar multifidus

The multifidus reaches upwards from the hip bones, sacrum and the mamilary processes to attach to the spinous process of a lumbar vertebrae two or more levels above.

Iliocostalis lumborum pars lumborum

The iliocostalis lumborum pars lumborum is a subsection of the iliocostalis lumborum. This portion of the muscle extends upwards from the back of the hip crest to attach to the tips of the lumbar transverse processes.

Longissimus thoracis pars lumborum

The longissimus thoracis pars lumborum is a subsection of the longissimus thoracis. It extends upwards from the back of the hip crest to attach to the lumbar transverse processes.

Serratus posterior inferior

The serratus posterior inferior reaches downwards and inwards from the bottom four pairs of ribs. It attaches to the lower two thoracic vertebrae. It also attaches to the spinous process of the upper two lumbar vertebrae.

Latissimus dorsai

The lattisimus dorsai reaches down from the inner aspect of the humerous to attach to the spinous processes of the lumbar vertebrae. (It also has attachments to the hip bones, the spinous processes of the lower thoracic vertebrae and the lower three ribs.)

Gluteus maximus

Again, if we include the sacrum as part of the lumbar spine, then we can also include the gluteus maximus in this list of muscles.

As an added incentive to include the gluteus maximus as a lower back muscle, the latissimus dorsai has some fibers that cross the midline at about the level of the sacrum or L5 to blend with fibers of the opposite side gluteus maximus.

Deeper muscles

There are also deeper muscles that attach between adjacent vertebrae. These include the intertransverse muscles which attach between the transverse processes of adjacent lumbar vertebrae and the interspinalis which attach between the spinous processes of adjacent lumbar vertebrae.

The transverse abdominis

Another muscle that attaches directly to the lumbar vertebrae is the transverse abdominis. This muscle wraps around the waist from front to back. It's fibers pass behind the quadratus lumborum and psoas and in front of the longissimus and iliocostalis muscles.

Muscles that cross in front of the lower back

Muscles that cross in front of the lumbar spine include the internal obliques, external obliques and the rectus abdominis.

The external obliques pass forwards downwards from the ribs to attach to the hip bone and the linea alba.

The internal obliques pass downwards and rearwards from the ribs to attach to the hip bones.

Muscles that cross in back of the lower back

Muscles that cross the back of the lumbar spine include the iliocostalis lumborum pars thoracis and longissimus thoracis pars thoracis.

Iliocostalis lumborum pars thoracis

Iliocostalis lumborum pars thoracis is the thoracic subsection of the iliocostalis lumborum. This muscle extends upwards from the back of the hip crest to attach to the backs of the lower 9 ribs.

Longissimus thoracis pars thoracis

Longissimus thoracis pars thoracis is the thoracic component of the longissimus thoracis. It reaches upwards from the back of the sacrum, plus from the spinous processes of the lower three lumbar vertebrae to attach to the transverse processes of the thoracic vertebrae as well as the backs of the ribs.

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