Are There Tendons in Your Back?

Your back contains dozens of tendons, though they look and behave quite differently from the thick, rope-like tendons you might picture in your knee or ankle. The deep muscles running along your spine attach to individual vertebrae through short, sometimes surprisingly thin tendons, while the large surface muscles of your back connect through broad, flat sheets of tendon-like tissue called aponeuroses. Understanding this anatomy matters because these structures play a central role in spinal stability, load transfer, and, for many people, chronic low back pain.

Why Back Tendons Look Nothing Like an Achilles

When most people think “tendon,” they imagine something like the Achilles tendon: a thick cord you can feel through the skin, connecting a powerful muscle to a bone. Back tendons are a different animal. Researchers who have studied the paraspinal muscles describe a “paradoxical” anatomy where the muscles themselves are large but their tendons are remarkably small relative to the muscle size. The erector spinae group, the long columns of muscle flanking your spine, has individual muscles with cross-sectional areas of roughly 9 to 10 square centimeters, yet the tendons attaching them can have ratios of tendon-to-muscle area as tiny as 1-to-739.¹ That means some of these tendons are hundreds of times smaller than the muscles pulling on them.

This is the opposite of what you see in limb tendons. In your arms and legs, tendons are often substantial structures designed to transmit large forces across joints and, in some cases, store elastic energy during movement. Back tendons don’t need to do that kind of work. Instead, they anchor muscles to vertebrae at very short distances, and much of the force transmission in the back happens through other connective tissue structures rather than through tendons alone.

The Deep Spinal Muscles and Their Tendons

The muscles closest to your spine are the ones with the most obvious tendons, even if those tendons are small. The multifidus is worth singling out because it sits right along the spinous processes (the bony bumps you can feel down the center of your back) and plays a critical role in stabilizing individual vertebrae during movement. In the lumbar spine, the multifidus has thick tendons at the spinous processes, and the muscle is organized into five overlapping bands that span several vertebral levels.² Researchers have built three-dimensional models of the lumbar multifidus to map out these tendon-muscle arrangements in detail, measuring fiber bundle length, fiber angle, and tendon length for each segment.³

The erector spinae group, which includes the longissimus and iliocostalis muscles, also attaches to the spine and ribs through tendons, but many of those attachments blend into a shared connective tissue sheet called the erector spinae aponeurosis. This is a dense band of longitudinally oriented collagen fibers, roughly 1.85 millimeters thick on average, that acts as a common tendon for the erector spinae complex in the lumbar region.⁴ So rather than having a clean, discrete tendon at each attachment point, the erector spinae muscles funnel their force through a shared sheet that then anchors to the pelvis and sacrum. This arrangement is part of why people sometimes say the back “doesn’t really have tendons”: the tendons are there, but they merge into broader structures that don’t look like the tendons in an anatomy textbook illustration of the hand or foot.

Surface Muscles of the Back Have Tendons Too

The more superficial muscles, the ones you can see on a well-muscled back, also have tendons, though again, they tend to be flat and sheet-like rather than cord-like. The trapezius, the large diamond-shaped muscle covering the upper and middle back, comes together as a distinct tendinous confluence in its lower portion. Anatomical dissections show that the lower trapezius is separate from the middle trapezius and converges into a tendon that surgeons sometimes harvest for tendon transfer procedures to repair damaged shoulder tendons.⁵ The triangular aponeurosis of the middle trapezius typically spans from about the fifth cervical vertebra to the first thoracic vertebra, while the lower trapezius extends down to around the tenth thoracic vertebra.

The latissimus dorsi, the broad muscle that sweeps from your lower back and pelvis up to your arm, is another example. It connects to the spine not through a single tendon but through tendinous fasciae that attach along the thoracic and lumbar vertebrae. Because it bridges the spine and the upper arm bone, tightness or dysfunction in the latissimus dorsi can cause problems in both directions: shoulder pain from poor joint mechanics, or tendinitis where the tendinous attachments meet the spine.⁶

The Thoracolumbar Fascia and Why It Gets Confused with Tendons

One of the most important connective tissue structures in the back is the thoracolumbar fascia, or TLF. It’s a multi-layered sheath that wraps around the paraspinal muscles and connects to the spine, the pelvis, and several of the large back and abdominal muscles. The TLF is sometimes described as a “tendon equivalent” for the trunk, because it transmits forces between the upper body and the lower body in ways that individual tendons do in the limbs. It plays a significant role in lumbar spine stability.⁷

Structurally, the TLF is an irregular dense connective tissue, averaging about 0.95 millimeters thick, while the erector spinae aponeurosis underneath it is roughly twice as thick.⁴ Despite being thin, the TLF is tough and mechanically important. It distributes loads across the trunk so that no single tendon or muscle has to bear the full brunt of, say, lifting a heavy box from the floor. This is part of why speaking about “back tendons” as isolated structures misses the picture. In the back, tendons, aponeuroses, and fascia work together as an integrated system, and the fascial component carries a substantial share of the mechanical load.

Back Fascia and Tendons as a Source of Pain

If you’ve ever had low back pain, there’s a reasonable chance your thoracolumbar fascia was involved. Research over the past two decades has established that the TLF is densely packed with sensory nerve endings, many of which are pain-sensing fibers. A systematic review of fascial innervation found that the TLF is the most-studied fascia in the body, and every study identified free nerve endings running through its layers.⁸ Detailed mapping in both rats and humans has shown that the outer layer and the subcutaneous tissue overlying the TLF carry the heaviest concentration of sensory fibers, including fibers containing substance P, a molecule closely associated with pain signaling. Substance P-positive nerve endings were found almost exclusively in these outer layers, which led researchers to conclude the TLF may play an important role in low back pain.⁹

This finding was reinforced by studies showing that the only type of nerve ending found in the TLF is the free nerve ending, with no specialized pressure or vibration receptors. An exclusive innervation with free nerve endings points strongly toward a pain-sensing function, though some of these endings have low mechanical thresholds, meaning they could also contribute to proprioception (your body’s sense of where it is in space).¹⁰

Functionally, changes in the TLF appear to track with chronic low back pain. People with chronic low back pain show reduced fascial shear strain compared to pain-free individuals: about 56% versus 70% in one ultrasound study.¹¹ Shear strain measures how freely the fascial layers glide over one another, and reduced gliding means the layers are sticking together or stiffening. A separate imaging study found that in people with chronic low back pain, the TLF becomes homogeneously thicker and loses its normal directional variation in thickness, a phenomenon the researchers described as a “frozen back.”¹² The fascia essentially remodels in a way that makes it stiffer and less adaptable, which could contribute to ongoing pain and restricted movement.

How Back Tendons and Fascia Respond to Loading

Tendons throughout the body are not static structures. They remodel in response to how you use them. Physical activity increases both the production and the breakdown of collagen in tendons, and chronic loading from regular exercise can lead to net collagen synthesis, making the tissue stiffer and more resistant to damage.¹³ This adaptation process applies to the tendons and connective tissues of the back just as it does elsewhere.

Tendon adaptation to mechanical stimuli can include changes in tendon dimensions, internal structure as seen on imaging, mechanical stiffness, and blood flow.¹⁴ For your back, this means that progressive loading through exercise can strengthen the tendinous and fascial structures supporting your spine. Conversely, prolonged inactivity may lead to weaker, less resilient connective tissue. The “frozen back” phenomenon described in chronic low back pain patients may represent a form of maladaptive remodeling, where inflammation or disuse causes the fascia to thicken and stiffen in a way that hurts rather than helps.

This is where the line between tendon problems and fascial problems gets blurry in the back. In your shoulder or elbow, a doctor can identify a specific tendon that’s inflamed or torn. In your back, the relevant structures merge into one another, so dysfunction in the erector spinae aponeurosis, the TLF, or the small multifidus tendons can all produce overlapping symptoms. This interconnectedness makes back pain notoriously difficult to localize.

Seeing Back Tendons on Imaging

Both MRI and ultrasound can visualize tendons and ligaments throughout the body, and these techniques have been validated against surgical findings and tissue samples.¹⁵ On MRI, a healthy tendon appears dark (low signal intensity) because its tightly packed collagen fibers don’t generate much signal. On ultrasound, a healthy tendon shows a characteristic bright, striped pattern.¹⁶

For the back specifically, MRI provides the broadest anatomical overview and is considered the gold standard for soft tissue contrast, making it well-suited for seeing the relationship between paraspinal muscles, their tendons, and the surrounding fascia. Ultrasound, meanwhile, has higher resolution for individual structures, can be performed quickly, and allows the clinician to watch tissues move in real time. Ultrasound is increasingly used to evaluate the TLF in people with low back pain, as it can measure fascial thickness and gliding in ways that correlate with symptoms. When clinicians talk about diagnosing “back tendon” problems, they’re usually looking at this broader network of tendons, aponeuroses, and fascia together rather than isolating a single tendon.

What Happens to Back Fascia and Tendons During Surgery

Spinal surgery almost always involves cutting through the thoracolumbar fascia and the paraspinal muscle attachments to access the vertebrae. Surgeons routinely close the posterior fascial layer at the end of the procedure, but the healing process doesn’t always restore the tissue’s original properties. Post-operative healing may result in suboptimal remodeling, structural failure at the repair site, or altered mechanical behavior of the fascia. Because the TLF plays a biomechanical role in load transfer between the trunk and the legs, impaired fascial gliding and structural defects after surgery can lead to local inflammation, sensitization of nerve endings, and ongoing functional problems.¹⁷

Computational modeling supports this concern. When researchers simulated the effects of incisions and adhesions in the TLF, they found that both significantly reduced cross-directional load sharing and overall tissue stiffness. The direction of the surgical cut matters: incisions aligned with the native collagen fiber direction preserved more of the fascia’s load-bearing function than incisions cutting across the fibers.¹⁸ Incorporating anisotropic (direction-dependent) TLF models into spine simulations showed that the fascia effectively stabilizes the spine by reducing how much individual vertebrae rotate. This research suggests that current standard surgical approaches, which disrupt the fascia’s fiber continuity, may contribute to the persistent pain some patients experience after spine surgery.

How Upright Posture Shaped the Back’s Tendon System

The unusual anatomy of back tendons makes more sense when you consider that the human spine evolved to bear loads vertically. Studies comparing back muscle activity during bipedal walking in humans and other primates suggest that the shift to habitual upright walking didn’t require a radical reinvention of back muscle function. Instead, it involved improvements in the mechanical advantages and architecture of the muscles that were already there.¹⁹

In four-legged animals, the back muscles and their connective tissues need to resist gravity pulling the spine downward between the front and hind limbs, like a suspension bridge. In humans, the spine is stacked vertically, so the paraspinal muscles work more to fine-tune balance and control rotation than to fight gravity directly. This may help explain why back tendons are so small relative to the muscles: the muscles don’t need to transmit huge forces through long tendons the way limb muscles do. Instead, they make constant small adjustments, and the broad fascial system handles the job of global load distribution. The trade-off is that this system is mechanically sensitive to disruption, which is one reason back injuries and back pain are so common and so persistent in a species that spends its days upright.