Medical Term Glossary
Plain-language explanations of the medical terms that appear on CT, MRI and X-ray reports — what each one means, when it matters, and what to ask your doctor.
C
D
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normal
Degenerative changes
A general term radiologists use for the everyday wear-and-tear that accumulates in the spine over a lifetime — slightly flattened cushions between vertebrae, small bony ridges along the edges, and a bit of joint thickening. Extremely common after the mid-30s and found in plenty of people who have no back pain at all.
Also: age-related changes, degeneration, degenerative disease
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normal
Disc bulge
A gentle, broad outward swell of one of the soft cushions that sit between the bones of the spine. The cushion stays intact — nothing has torn or leaked — but its outer edge pushes a little past its usual footprint. Extremely common with age and often found in people who have no symptoms at all.
Also: annular bulge, broad-based bulge, bulging disc
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warning
Disc herniation
A small tear in the outer wall of one of the spinal cushions has let some of the soft inner core push outward into a focused lump. Unlike a broad, even bulge, this is a localized pocket that can press on a nearby nerve and cause arm or leg pain, tingling, or weakness along the nerve's path.
Also: disc extrusion, disc protrusion, herniated disc
F
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Facet joint
One of the small paired joints at the back of each level of the spine that link one vertebra to the next. They guide and limit movement — bending, twisting, leaning back — and share load with the disc at the front. Like every joint in the body, they can show wear over time.
Also: apophyseal joint, facet, facet arthropathy
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warning
Foraminal narrowing
A tightening of one of the small side-doors of the spine that each nerve uses to leave the spinal canal and travel out to the body. When the door is smaller than usual, the nerve passing through can be pinched, leading to pain, tingling, or weakness along that nerve's path — usually on one side.
Also: exit foramen narrowing, foraminal stenosis, narrowing of the nerve exit
O
S
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warning
Spinal canal stenosis
A narrowing of the bony tunnel that houses the spinal cord and nerve roots. The narrowing crowds the structures running through it, which can cause back pain, leg pain, numbness, or weakness depending on the level. Most cases develop slowly with age; the severity on imaging often correlates loosely with symptoms.
Also: central canal narrowing, central canal stenosis, cervical stenosis
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warning
Spondylolisthesis
One of the bones in the spine has shifted forward, backward, or sideways relative to the bone below it, so the stack no longer lines up perfectly. The slip is often small and stable, but a larger shift can narrow the spinal canal or pinch a nerve, causing back pain or symptoms down a leg.
Also: anterolisthesis, degenerative spondylolisthesis, isthmic spondylolisthesis
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normal
Spondylosis
A general term for the slow, age-related wear of the spine — drying cushions, small bony spurs, and stiffer joints. It is the back's version of grey hair: nearly universal after middle age, often visible on scans of people who feel completely fine, and usually a description of normal ageing rather than a disease.
Also: arthritis of the spine, cervical spondylosis, degenerative disc disease
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