Understanding spine anatomy and common disc conditions helps patients ask better questions and navigate their care more confidently. Terms like annulus fibrosus, nucleus pulposus, and discogenic pain describe structures and symptoms that vary considerably between individuals. This glossary defines key terms our clinical team uses when evaluating candidates for non-surgical disc treatment options.

When your specialist mentions a herniated disc, annular tear, or radiculopathy, knowing what those terms mean helps you participate in treatment decisions with greater clarity. The definitions below reflect the anatomy and conditions our team considers when determining whether non-surgical options may be appropriate for a given patient.

Annulus Fibrosus

The annulus fibrosus is the tough, fibrous outer ring of an intervertebral disc. Composed of multiple layers of strong collagen fibers arranged in concentric rings, this structure encases the softer, gel-like nucleus pulposus within the disc, providing stability and containing the disc’s internal pressure. When healthy, the annulus fibrosus is essential for maintaining disc integrity, absorbing shock, and allowing spinal flexibility. Tears in this outer ring — often due to injury or degeneration — may become a significant source of chronic back pain. Annular repair is a primary target for non-surgical regenerative treatments in candidates where imaging and evaluation confirm the tear as a pain generator.

Nucleus Pulposus

The nucleus pulposus is the soft, gel-like core located at the center of each intervertebral disc. Rich in water content, this resilient material acts as the primary shock absorber for the spine, distributing pressure across the vertebrae during movement and weight-bearing activities. Its pliable nature allows the spine to bend and twist while providing cushioning against impact. When the surrounding annulus fibrosus is compromised by a tear, the nucleus pulposus may bulge or herniate beyond its normal boundaries, potentially leading to nerve compression and pain. Maintaining the integrity of both disc components is important to overall spine health.

Intervertebral Disc

An intervertebral disc is a specialized cushion-like structure situated between most of the vertebrae in your spinal column. Each disc serves as a shock absorber, protecting the bones from impact during daily activities like walking, running, and lifting. These discs also facilitate flexibility and mobility of the spine, allowing for a wide range of motion. Each disc comprises an outer fibrous ring (the annulus fibrosus) and an inner gel-like core (the nucleus pulposus). Damage or degeneration of an intervertebral disc is a common source of chronic back and neck pain and a key focus for non-surgical treatment evaluation.

Vertebra

A vertebra is any of the individual bones that make up your spinal column. The human spine typically consists of 33 vertebrae stacked one upon another, separated by intervertebral discs. These bones provide the main structural support for your body, protect the spinal cord and nerve roots, and serve as attachment points for muscles and ligaments. Vertebrae are categorized by region: cervical (neck), thoracic (mid-back), lumbar (lower back), sacrum, and coccyx. The health and alignment of these bones are fundamental to posture, movement, and nervous system function.

Foramen

A foramen (plural: foramina) is a natural opening or passageway in the spine. The intervertebral foramen refers specifically to the small openings on each side of the spinal column, between adjacent vertebrae, through which spinal nerves exit the spinal canal to reach other parts of the body. When conditions such as disc herniation, bone spurs, or spinal stenosis narrow these openings, the exiting nerves may be compressed. That compression may cause pain, numbness, tingling, or weakness in the areas served by the affected nerve — a pattern known as radiculopathy.

Facet Joint

Facet joints are small, paired joints located on the back of each vertebra, connecting adjacent vertebral segments. They guide and limit spinal movement — allowing bending, twisting, and rotation while helping prevent excessive motion that could damage the spinal cord or nerves. Like other joints in the body, facet joints contain cartilage and a joint capsule, making them susceptible to arthritis, inflammation, and degeneration over time. When these joints become inflamed or damaged, they may become a significant source of localized back pain, particularly with certain movements or postures.

Annular Tear

An annular tear is a rip or fissure in the annulus fibrosus — the tough outer ring of an intervertebral disc. These tears vary in size and depth, ranging from small fissures to full-thickness ruptures. Annular tears are a recognized cause of chronic low back pain in many patients, often because they allow inflammatory chemicals from within the disc’s nucleus to leak out and irritate nearby spinal nerves. Unlike most tissues in the body, the intervertebral disc has a very limited blood supply, which means annular tears may struggle to heal without intervention. Identifying and addressing these tears is central to treating persistent discogenic pain and may slow further degeneration. Learn more about how annular tears cause chronic low back pain.

Degenerative Disc Disease (DDD)

Degenerative Disc Disease (DDD) refers to the progressive breakdown of one or more intervertebral discs over time. Despite its name, DDD is a condition — not a disease in the traditional sense — and reflects changes that may occur with aging, though it may also be accelerated by injury or genetics. Characteristic changes include loss of disc height, reduced hydration (desiccation), and the development of annular tears. These changes may reduce shock absorption, create instability, and contribute to pain. Not all disc degeneration causes symptoms, but DDD is a common underlying factor in chronic back pain, and many patients with this diagnosis explore treatments aimed at restoring disc function.

Herniated Disc

A herniated disc occurs when the soft, gel-like nucleus pulposus pushes through a tear in the annulus fibrosus and extends beyond normal disc boundaries. This condition is also referred to as a ruptured or slipped disc. When disc material herniates, it may press on nearby spinal nerves or the spinal cord, causing pain, numbness, tingling, or weakness in the areas those nerves serve. Herniations are a common contributor to radiculopathy and sciatica. Non-surgical disc treatment options, including biologic disc repair, may address the underlying annular tear in appropriate candidates. See how herniated discs differ from bulging discs and what relief options may apply.

Bulging Disc

A bulging disc describes a situation where the intervertebral disc extends beyond its normal perimeter, similar to a tire with low air pressure. Unlike a herniated disc, where the nucleus pulposus breaks through the annulus fibrosus, a bulging disc keeps the annulus intact — the disc material remains contained. While often asymptomatic, a significant disc bulge may press on nearby spinal nerves or contribute to spinal stenosis. Bulging discs represent an early stage of disc degeneration and may progress to a herniation in some cases, underscoring the value of early evaluation and conservative or regenerative care.

Sciatica

Sciatica is a type of radiculopathy characterized by pain that radiates along the path of the sciatic nerve — the longest nerve in the body, originating from nerve roots in the lower back, traveling through the buttocks, and extending down the back of each leg. Sciatica typically affects one side of the body and may manifest as sharp, shooting pain, burning, numbness, tingling, or weakness anywhere along this pathway. Common causes include herniated discs, spinal stenosis, and bone spurs that compress the sciatic nerve roots in the lumbar spine. Sciatica is a symptom, not a standalone diagnosis, and the underlying cause guides treatment decisions. Explore common myths about sciatica and non-surgical relief options.

Radiculopathy

Radiculopathy refers to a set of symptoms caused by compression, inflammation, or irritation of a spinal nerve root. These symptoms typically include pain, numbness, tingling, or weakness that travels along the specific nerve pathway from the spine to another part of the body. Cervical radiculopathy affects the neck and arms; lumbar radiculopathy impacts the lower back, buttocks, and legs. Common causes include herniated discs, bone spurs (osteophytes), spinal stenosis, and disc degeneration that narrows the space around a nerve root. Treatment focuses on identifying and relieving pressure on the affected nerve root through conservative management or targeted interventions appropriate to each patient’s case.

Discogenic Pain

Discogenic pain refers to pain that originates directly from a damaged or degenerated intervertebral disc, rather than from nerve compression. This pain is typically felt deep in the back, often described as a dull ache, and may worsen with activities that load the disc — such as prolonged sitting, bending forward, lifting, or coughing. The source is believed to be internal disc disruption, including annular tears, inflammation within the disc, or degeneration of the disc’s internal structures. Diagnosing discogenic pain often requires specific diagnostic procedures. In appropriate candidates, treatments such as biologic disc repair may target the underlying disc pathology to support lasting relief.

Spinal Stenosis

Spinal stenosis is a condition characterized by narrowing of the spinal canal — the bony passageway housing the spinal cord and nerve roots — or narrowing of the foramina where nerves exit the spine. This narrowing may result from degenerative disc disease, bulging or herniated discs, thickened ligaments, bone spurs, or facet joint arthritis. As the spaces narrow, the spinal cord or nerve roots may be compressed, producing symptoms such as pain, numbness, tingling, and leg weakness. Walking or standing often aggravates symptoms; leaning forward or sitting may provide temporary relief. Non-surgical options are evaluated on a case-by-case basis, and candidacy depends on the degree of narrowing, symptom severity, and individual patient factors. Learn more about the common symptoms of spinal stenosis.

Expert Take

Understanding these terms is a starting point — not a self-diagnosis tool. Our clinical team evaluates each patient individually, using imaging, clinical history, and functional assessment to determine whether a specific condition is generating pain and whether non-surgical treatment may be an appropriate option. Anatomy is consistent across patients; outcomes are not. Knowing your anatomy helps you ask better questions — our job is to provide honest answers specific to your case.

To continue building your understanding of spine care options, we recommend: A Glossary of Key Terms in Regenerative Spine Treatment