The spine isn’t a single joint, but it contains over 70 joints working together. Every pair of vertebrae connects through multiple joint surfaces, making the spinal column one of the most joint-dense structures in your body. It’s more accurate to think of the spine as a chain of joints rather than a single bone or a single joint.
Two Types of Joints in the Spine
Each pair of vertebrae connects at three separate points: one joint between the vertebral bodies (the thick, round front portions) and two facet joints at the back. These two joint types have completely different structures and serve different purposes.
The joints between vertebral bodies are cartilaginous joints. Instead of a fluid-filled cavity, they’re connected by intervertebral discs, which are thick pads of fibrocartilage. These are the principal load-bearing joints of the spine, designed to absorb shock and resist compression from body weight, gravity, and impact. Each disc has a gel-like center that retains water and provides cushioning, surrounded by concentric rings of collagen fibers oriented in alternating directions. That layered design lets the disc resist forces from multiple directions at once.
The facet joints (also called zygapophysial joints) are synovial joints, structurally similar to your knee or shoulder. They have a joint capsule, a lining that produces synovial fluid, and smooth cartilage covering the bone surfaces. Each vertebra has four facet joints: two connecting to the vertebra above and two to the vertebra below. These joints guide and limit how the vertebrae move relative to each other, controlling how far you can twist, bend, and arch.
How Spinal Joints Create Movement
No single spinal joint moves very much on its own. The flexibility you feel when you bend or twist comes from small amounts of motion at dozens of joints adding up. How much total movement you get depends on which region of the spine you’re looking at.
The neck is the most mobile section. Healthy young adults typically have about 58 degrees of forward bending and 59 degrees of backward extension in the cervical spine, plus roughly 70 degrees of rotation to each side. That rotation is what lets you look over your shoulder.
The lower back allows about 70 degrees of forward bending but only around 38 degrees of rotation in each direction, about half the turning range of the neck. The thoracic spine (mid-back) is the least mobile section overall because the rib cage physically restricts how far those vertebrae can move.
These differences exist because the facet joints in each region are oriented differently. In the neck, the facet surfaces are angled to permit rotation. In the lower back, they’re oriented more vertically, favoring forward and backward bending while limiting twisting. The shape of the joint surfaces essentially acts as a built-in movement guide for each spinal segment.
When Spinal Joints Cause Pain
Because the spine contains two distinct joint types, back pain can originate from either one, and the symptoms feel different depending on which is involved.
Facet joint pain is typically a dull ache or stiffness localized to one area of the back. It tends to get worse with movements that load the facet joints: arching backward, twisting, or standing for long periods. It often feels stiffest after rest or prolonged sitting and may improve once you start moving in ways that take pressure off those joints. Imaging can sometimes reveal bone spurs or joint enlargement at the affected facet joints.
Disc-related pain behaves differently. Because intervertebral discs sit right next to the spinal nerves, a bulging or herniated disc can compress a nerve and send pain radiating down the leg, sometimes with tingling, numbness, or weakness. This is the mechanism behind sciatica. Disc pain tends to worsen with bending forward, sitting, or lifting, all movements that increase pressure on the front of the spine where the discs sit.
Both types of spinal joint degenerate with age. The discs gradually lose water content and height, while the facet joints develop the same kind of cartilage wear you’d see in an arthritic knee. These changes are nearly universal in people over 50 and don’t always cause symptoms, but when they do, identifying which joint type is the source of pain matters for choosing the right treatment approach.
Why the Spine Works as a System
The two joint types in the spine are mechanically interdependent. The intervertebral discs handle most of the compressive load from body weight and impact, acting as shock absorbers between the vertebral bodies. The facet joints handle about 16 to 30 percent of the spine’s compressive load, and their primary role is controlling and limiting motion. Together, they allow the spine to be both strong enough to support your upper body and flexible enough to let you bend, twist, and move in virtually every direction.
When one joint type deteriorates, it shifts extra stress onto the other. A disc that loses height, for instance, changes the alignment of the facet joints above and below it, accelerating wear on those joints. This is why spinal degeneration rarely stays isolated to one structure. The whole system is designed to share the load, and when one part weakens, the neighboring joints compensate.