The thoracic and lumbar spine connect at one of the more important locations in the body. The thoracolumbar junction is the place where the bottom thoracic vertebra (T12) meets the top lumbar vertebrae (L1). This is also the attachment point for many of the body’s key muscles.
My favorite muscle, the psoas, attaches on both of these points. The large back muscles the latissimus dorsi and trapezius have attachments on T12. The diaphragm, while not attaching at either of these spots lives in the neighborhood. The cauda equina, a bundle of nerves at the end of the spinal cord, also known as the horses tail, is found anywhere from T12 to L3 in adults.
The thoracolumbar joint is a particularly troubling spot in the skeletal system. A great deal of the postural dysfunction that I see in my clients occurs at this meeting area. All too often as people stand before me it is as if they are leaning slightly backwards at this exact spot. I think this is due to poor skeletal alignment in the pelvis and legs but it manifests here in a disconcerting manner.
This juncture of the thoracic and lumbar spine is interesting for a number of reasons. The two sections of the spine are very different from each other which can make for a tricky transition. The interlocking facet joints that allow for the movements of the spine are aligned differently at the meeting place of T12/L1 which adds to the instability of the joint.
Also, there is very little twist in the lumbar spine while the thoracic is capable of a great deal of rotation. The ribcage puts the brakes on too much rotation but the ability for the thoracic spine to twist is in marked contrast to the lumbar spine. There is no rotation in the lumbar because of its weight bearing responsibilities.
In a way we can look at the spine as having two halves. The upper half is the cervicothoracic and the lower half is the lumbosacral. The junction of T12/L1 marks the meeting of these two halves. I often teach that we are looking for two qualities in the spine—the ability to move each vertebrae in a chain like cat and cow, and the ability to solidify the spine as a solid pole as in a successful plank.
This less than smooth transition point between the thoracic and lumbar spine makes this a much more complicated proposition which is why this area of the spine is prone to dysfunction. I often refer to it as a collapse at T12 and to me, this is why so many people are shallow breathers depending too much on the thoracic cavity for their breathing technique.
There is an inherent instability in the shift from the stable lumbar to the movable thoracic, and poor alignment in the pelvis and legs often allows the weight of the upper body to fall backwards at the exact spot where T12/L1 meet.
This insecurity is non-negotiable—it is a function of the body that we must be aware of. The only way for this dicey transition to be handled successfully is if all of the bones below the thoracolumbar joint are well aligned.
There are so many reasons why we need good posture. Providing support to the thoracolumbar joint ranks very high on the list.