The thoracic spine is the middle section of your backbone, made up of 12 vertebrae labeled T1 through T12. It runs from the base of your neck down to the bottom of your ribcage, and every one of your ribs attaches to it. This makes the thoracic spine structurally unique: it’s the only part of your spine that connects directly to your rib cage, giving your upper body its shape and protecting the organs inside your chest.
Where It Sits in Your Spine
Your spine has three main regions. The cervical spine (your neck) sits on top with 7 vertebrae. Below that is the thoracic spine with its 12 vertebrae. And at the bottom, the lumbar spine (your lower back) has 5 vertebrae. The thoracic section is the longest segment, spanning roughly the middle of your back from shoulder level down to where your lowest ribs end.
Each thoracic vertebra has a distinctive heart-shaped body and a roughly circular opening in the center called the vertebral foramen. Your spinal cord threads through those openings, so the vertebrae act like a bony tunnel protecting the nerve tissue inside.
How the Ribs Attach
The defining feature of the thoracic spine is its connection to the ribs. Each vertebra has small, smooth facets on its body and on a bony bump called the transverse process. The head of a rib fits against the vertebral body, and the rib’s tubercle fits against the transverse process, creating two joints per rib on each side.
Most ribs share their attachment between two neighboring vertebrae. Ribs 2 through 9 each straddle the junction between the vertebra of the same number and the one above it. The first rib and ribs 10 through 12 are different: each connects to only a single vertebra. This dual-joint system locks the ribs firmly in place while still allowing the small gliding movements you need for breathing.
What It Protects
Together, the thoracic spine and the rib cage form the walls of your thoracic cavity, the enclosed space in your chest. That cavity houses your heart, lungs, trachea (windpipe), esophagus, and thymus gland. The thoracic spine forms the back wall, your ribs wrap around the sides, and the sternum (breastbone) closes the front. This bony enclosure is remarkably effective at shielding your most vital organs from impact.
Range of Motion and Stiffness
If you’ve ever noticed that your mid-back doesn’t bend or twist as freely as your neck or lower back, the rib attachments are a big reason why. Those joints brace each vertebra and limit how far it can move. The total forward-and-backward range of the thoracic spine is roughly 32 degrees on average, measured from T1 down to the thoracolumbar junction.
Movement isn’t evenly distributed across all 12 levels. The upper thoracic segments near the neck (T1/T2) allow about 4 degrees of motion each, but the middle segments around T4/T5 contribute less than 1 degree each. Motion then gradually increases again as you move downward, with the T12/L1 junction contributing the most at about 4.2 degrees. This pattern means the stiffest part of your entire spine sits right in the middle of your upper back.
The Natural Curve
Your thoracic spine is supposed to curve. Viewed from the side, it rounds gently outward (toward the back of your body) in a curve called kyphosis. A healthy thoracic kyphosis falls between 20 and 40 degrees. Your cervical spine and lumbar spine curve in the opposite direction (inward, toward your belly), and these alternating curves work together to balance your head over your pelvis and absorb shock when you walk or run.
When the thoracic curve exceeds 40 degrees, it’s considered excessive kyphosis, sometimes called a “rounded back” or “hunchback” posture. One well-known cause in adolescents is Scheuermann’s disease, where at least three consecutive vertebrae develop a wedge shape of more than 5 degrees each, along with irregular endplates. This tilts the vertebrae forward and deepens the curve. In older adults, compression fractures from osteoporosis are the more common culprit.
The Spinal Canal Is Narrower Here
The bony channel that houses your spinal cord varies in size depending on the region. In the cervical spine, the canal averages about 17 mm across. In the thoracic spine, it starts at around 16 mm at T1 and then narrows to about 14 to 15 mm by T2, staying close to 15 mm from T3 through T11. It widens again at T12 to about 18 mm as it transitions into the roomier lumbar spine.
This relative narrowness matters. Because there’s less space around the spinal cord in the mid-back, even a small disc herniation or bone spur can put pressure on the cord. The thoracic spine also relies on a critical blood vessel, the artery of Adamkiewicz, which typically branches off the left side of the aorta between T9 and T11 and is the main blood supply to the lower spinal cord. Disruption of this artery during surgery or trauma can have serious neurological consequences.
Common Thoracic Spine Problems
Disc herniations in the thoracic spine are far less common than in the neck or lower back. Imaging studies show that 11 to 37 percent of people with no symptoms at all have some degree of thoracic disc bulging on an MRI, meaning most thoracic disc abnormalities never cause problems. Herniations that actually produce symptoms are estimated at roughly one in a million people per year, accounting for less than 4 percent of all disc herniations that need surgery.
When a thoracic disc herniation does cause symptoms, the picture can be confusing. The most common complaints are pain, numbness, and weakness in the legs (because the herniation presses on the spinal cord rather than a single nerve root, as in the lower back). But some people experience band-like chest pain, abdominal discomfort, or even symptoms that mimic heart or gastrointestinal problems. This makes thoracic disc issues notoriously tricky to diagnose.
Other conditions that affect this region include thoracic muscle strain (often from poor posture or prolonged sitting), compression fractures in people with weakened bones, and degenerative changes in the facet joints that connect one vertebra to the next. Pain between the shoulder blades is one of the most frequent complaints and is usually muscular rather than structural.
Why Posture Matters More Here
Because the thoracic spine already curves outward naturally, it’s particularly susceptible to postural changes. Hours spent hunched over a desk or phone gradually encourage the curve to deepen. Unlike the lumbar spine, which has large muscles and significant mobility to compensate for poor positioning, the thoracic spine is relatively rigid. Once it settles into a deeper curve, the surrounding muscles and ligaments adapt to that position, making it harder to straighten over time.
Strengthening the muscles between your shoulder blades, stretching the chest muscles, and practicing extension (gently arching your upper back backward) are the primary strategies for maintaining thoracic mobility. The goal isn’t to eliminate the curve but to keep it within that healthy 20 to 40 degree window and preserve the segment-by-segment motion that lets you rotate, reach, and breathe comfortably.