Understanding spine diagnostic terminology helps you have more informed conversations with your care team. This glossary defines key concepts — from annular tears and disc herniation to radiculopathy and discogenic pain — so you can better interpret imaging results and evaluate treatment options. Each patient’s condition is individual; these definitions provide context, not medical advice.

Annulus Fibrosus

The annulus fibrosus is the tough, outer ring of an intervertebral disc, made up of strong layers of collagen fibers. Its primary role is to contain the softer, gel-like nucleus pulposus within the disc and to provide structural stability and flexibility to the spine. When this outer layer sustains injury, it may develop tears or fissures — known as annular tears. These tears can be a source of chronic back pain, as they may allow inflammatory chemicals from the disc’s interior to leak out and irritate nearby spinal nerves. Identifying damage to the annulus fibrosus through specialized imaging or diagnostic procedures is often a key step in understanding the source of a patient’s pain and guiding appropriate treatment.

Nucleus Pulposus

The nucleus pulposus is the soft, gel-like inner core of an intervertebral disc. Rich in water, this central material acts as the spine’s primary shock absorber, distributing pressure across the vertebrae during movement and weight-bearing. When the surrounding annulus fibrosus is weakened or torn, the nucleus pulposus may migrate or push through the outer ring, contributing to disc bulging or herniation. These structural changes — often visible on MRI — can result in compression or irritation of nearby spinal nerves, producing pain, numbness, or weakness that may radiate into the limbs, a pattern known as radiculopathy.

Intervertebral Disc

An intervertebral disc serves as a cushion between each vertebra in the spinal column. These structures are composed of a tough outer ring (annulus fibrosus) and a soft, gel-like inner core (nucleus pulposus). Discs enable spinal flexibility, absorb shock, and distribute forces throughout the back. They are susceptible to degeneration and injury — both frequently identified through diagnostic imaging. Conditions such as degenerative disc disease, disc herniation, and annular tears are among the most common sources of chronic back and neck pain, making disc evaluation central to effective spine care.

Foramen

The neural foramen refers to the small bony opening on each side of the spinal column through which spinal nerves exit to travel to other parts of the body. These pathways allow nerve roots to extend from the spinal cord to the arms, legs, and torso, transmitting sensory and motor signals. When conditions such as disc bulging, herniation, bone spurs, or thickened ligaments narrow these openings, the exiting nerves may become compressed. This narrowing is often visible on MRI or CT scans and can produce pain, numbness, tingling, or weakness in areas supplied by the affected nerve — a condition known as radiculopathy.

Facet Joint

Facet joints are small, paired joints located at the back of each vertebra, connecting adjacent spinal bones. These joints allow controlled movement — bending and twisting — while providing stability. Like other joints in the body, facet joints can undergo degenerative changes over time, leading to conditions such as facet arthropathy. When these joints become inflamed or arthritic, they may be a source of localized back or neck pain, separate from disc-related issues. Evaluation typically involves physical examination, imaging such as X-rays or MRI, and sometimes diagnostic facet joint injections to clarify whether the facets are contributing to a patient’s symptoms.

Vertebra

A vertebra is one of the individual bones that make up the spinal column, which extends from the base of the skull to the pelvis. The human spine typically consists of 33 vertebrae, divided into cervical (neck), thoracic (mid-back), lumbar (lower back), sacral, and coccygeal regions. These bones protect the spinal cord, provide structural support, and serve as attachment points for muscles and ligaments. Diagnostic imaging — including X-rays, CT scans, and MRI — is routinely used to evaluate vertebrae for fractures, alignment problems, bone spurs, and degenerative changes that may contribute to pain and spinal dysfunction.

Annular Tear

An annular tear is a rip or fissure in the annulus fibrosus, the tough outer ring of an intervertebral disc. These tears are clinically significant because they may allow inflammatory chemicals from the nucleus pulposus to leak out, irritating nearby spinal nerves and contributing to persistent pain — often described as discogenic pain. Unlike many tissues, spinal discs have a limited blood supply, which means annular tears may struggle to heal on their own. While some tears are visible on advanced MRI, smaller or subtler tears often require a specialized diagnostic procedure — an annulargram — to precisely identify their location and determine whether they are the primary pain source. Learn more about annular tears as a root cause of chronic back pain.

Degenerative Disc Disease (DDD)

Degenerative Disc Disease (DDD) refers to the progressive breakdown of one or more intervertebral discs over time. Despite the term “disease,” it is a common condition associated with aging, characterized by gradual loss of disc height, reduced hydration (desiccation), and the development of annular tears. These changes can compromise the disc’s shock-absorbing function and may lead to instability and pain. DDD is frequently identified through MRI, which visualizes disc desiccation, height loss, and other structural changes. Understanding the extent and location of DDD helps evaluate its potential contribution to a patient’s chronic back or neck symptoms.

Herniated Disc

A herniated disc — sometimes called a “ruptured disc” or “slipped disc” — occurs when the soft nucleus pulposus pushes through a tear in the annulus fibrosus and extends beyond its normal boundary. This displaced disc material may compress or chemically irritate nearby spinal nerves or the spinal cord. The resulting nerve involvement can contribute to sciatica, radiculopathy, and significant localized pain. Herniated discs are typically diagnosed through physical examination combined with MRI, which provides detailed visualization of disc position and surrounding neural structures. See how herniated discs differ from bulging discs.

Bulging Disc

A bulging disc occurs when the intervertebral disc — or a significant portion of its circumference — extends beyond the normal boundaries of the adjacent vertebrae. Unlike a herniated disc, where the nucleus pulposus breaks through the outer annulus, in a bulging disc the nucleus pulposus remains contained while the annulus fibrosus stretches and deforms outward. Though generally less severe than a herniation, a bulging disc may still exert pressure on nearby spinal nerves, the spinal cord, or other sensitive structures in the spinal canal. MRI is highly effective at visualizing bulging discs and distinguishing them from herniations, helping to guide treatment planning.

Spinal Stenosis

Spinal stenosis is characterized by narrowing of the spinal canal or the nerve root passageways (foramina) within the spine. This narrowing may result from disc bulging or herniation, bone spurs (osteophytes) from degenerative arthritis, thickening of ligaments, or a combination of these factors. When the spinal canal or foramina narrow, they can compress the spinal cord or individual spinal nerves, producing pain, numbness, weakness, or tingling — often in the legs (lumbar stenosis) or arms (cervical stenosis) — that may worsen with standing or walking. Spinal stenosis is evaluated through MRI or CT scans, which measure the degree of narrowing and identify underlying causes. Explore common symptoms of spinal stenosis.

Sciatica

Sciatica describes pain that radiates along the path of the sciatic nerve, which extends from the lower back through the buttock and down the back of the leg. This distinctive symptom pattern — often sharp, shooting, burning, or electrical — may be accompanied by numbness, tingling, or weakness in the affected leg. Sciatica is not a standalone condition but a symptom of underlying nerve root compression, most commonly associated with a herniated disc, spinal stenosis, or bone spurs in the lower back. Diagnostic evaluation — including physical examination and MRI — helps identify the specific cause so that targeted treatment can be considered. Read about common myths around sciatica and non-surgical relief.

Radiculopathy

Radiculopathy is a neurological condition caused by compression, inflammation, or damage to a spinal nerve root as it exits the spinal column. Symptoms depend on which nerve root is affected. Cervical radiculopathy affects nerve roots in the neck and may produce pain, numbness, tingling, or weakness radiating into the shoulder, arm, or hand. Lumbar radiculopathy affects nerve roots in the lower back and may cause similar symptoms radiating into the buttock, leg, or foot — a pattern commonly called sciatica when it follows the sciatic nerve path. Diagnosis involves clinical assessment, sometimes nerve conduction studies, and MRI to visualize the site and cause of nerve involvement.

Expert Take

Accurate identification of the pain generator — whether disc, facet joint, or nerve root — is the foundation of any effective spine treatment plan. Imaging findings alone do not determine candidacy for any procedure; our clinical team evaluates each patient individually, correlating imaging with a thorough clinical presentation before recommending a treatment path.

Discogenic Pain

Discogenic pain refers to pain that originates directly from a damaged or degenerated intervertebral disc, rather than from nerve compression caused by displaced disc material. This type of pain is typically felt deep in the back and may worsen with activities that load the disc — sitting, bending, lifting, or coughing. Diagnosing discogenic pain can be challenging because it does not always produce obvious findings on standard MRI. Specialized diagnostic procedures such as an annulargram — in which contrast dye is injected into the disc to provoke pain and visualize internal tears — may be used to confirm the disc as the primary pain source in appropriate candidates.

Annulargram

An annulargram is a specialized diagnostic procedure used to identify tears or damage within the annulus fibrosus and to determine whether those tears are the source of a patient’s chronic back pain. A thin needle is guided into the suspected disc under fluoroscopic (live X-ray) guidance, and a small amount of contrast dye is injected. This allows clinicians to visualize internal tears and assess the disc’s structural integrity. When the injection reproduces the patient’s typical pain pattern, it provides evidence that the disc may be the primary pain source — making the annulargram a valuable evaluation tool for candidates being considered for targeted disc treatments.

If you would like to read more, we recommend this article: Diagnostic Imaging and Evaluation Terms for Spinal Health