Diffuse Idiopathic Skeletal Hyperostosis

Prepared and reviewed by the PrepElephant Academic Review Team

First published 14 Oct 2026 · Spot an error?

Reference basis: Apley's System of Orthopaedics and Fractures; Maheshwari's Essential Orthopaedics

On this page

Direct answer
What you must remember
Separating DISH from ankylosing spondylitis
Where the exam tries to catch you
Frequently asked questions
Related topics

Direct answer

Diffuse idiopathic skeletal hyperostosis is a non-inflammatory condition in which bone flows along the anterolateral surface of the spine, involving at least four contiguous vertebral bodies while the disc spaces remain relatively preserved. It is also called Forestier disease and is most often seen in older men. Most people are asymptomatic, though stiffness, dysphagia from anterior cervical osteophytes and fractures of the rigid spine after minor trauma can occur.

What you must remember

Diagnostic criteria: flowing ossification along the anterolateral vertebral bodies in at least four contiguous segments, with preserved disc height at those levels.
Sacroiliac joints: spared in this condition; erosion, sclerosis or fusion points instead to ankylosing spondylitis.
Demographics: mainly older men, with associations with diabetes, obesity and metabolic syndrome.
Location: the thoracic spine is most often involved, and cervical involvement can cause dysphagia.
Extraspinal features: enthesopathic ossification such as calcaneal spurs, and bony change at the pelvis or elbow, may accompany the spinal disease.
Complication: the rigidly ossified spine fractures easily after minor trauma, with a risk of unstable injury and cord damage.
Management: analgesia with NSAIDs and physiotherapy; surgery is reserved for dysphagia from large osteophytes or an unstable fracture.

Separating DISH from ankylosing spondylitis

A 64-year-old diabetic man has a stiff back and dysphagia, and a lateral radiograph shows bridging ossification over several thoracic vertebrae. Both DISH and ankylosing spondylitis can bridge the spine, so the features in the table decide which diagnosis fits.

Feature	DISH	Ankylosing spondylitis
Ossification pattern	Flowing, bridging, candle-wax appearance	Syndesmophytes and bamboo spine
Disc spaces	Relatively preserved	Often preserved early, may narrow late; vertebrae become squared
Sacroiliac joints	Spared	Erosion, sclerosis and fusion
Typical patient	Older men, often with diabetes or obesity	Young men, HLA-B27 associated

Spared sacroiliac joints with preserved disc height favour DISH, while sacroiliitis with syndesmophytes points to ankylosing spondylitis. The examiner expects you to name the sacroiliac findings, not just the bridging. Radiographs of the spine and both sacroiliac joints often settle the question together, because a bridged spine with normal sacroiliac joints points to DISH.

Disc height is the easiest feature to miss on a lateral view. Checking it at each bridged level prevents the common error of calling a spondyloarthropathy.

Where the exam tries to catch you

Examiners test whether you can separate a spinal bridge from a spondyloarthropathy and manage the complications.

Trap: diagnosing ankylosing spondylitis from spinal bridging alone. Correct: DISH bridges the spine but spares the sacroiliac joints, so sacroiliac imaging is the discriminating feature.
Trap: operating on DISH for stiffness. Correct: most patients are managed with analgesia and physiotherapy, and surgery is for dysphagia or unstable fracture.
Trap: dismissing spinal pain after a minor fall. Correct: the rigid ossified spine fractures easily, so imaging after trauma is essential.

Frequently asked questions

What are the criteria for diffuse idiopathic skeletal hyperostosis?

The Resnick criteria for diffuse idiopathic skeletal hyperostosis require flowing ossification along the anterolateral aspect of at least four contiguous vertebral bodies, preserved disc height at those levels, and no sacroiliac erosion, sclerosis or fusion. Meeting all three distinguishes it from ankylosing spondylitis and degenerative spondylosis.

Why is diffuse idiopathic skeletal hyperostosis confused with ankylosing spondylitis?

Both conditions cause bridging ossification of the spine and stiffness, but diffuse idiopathic skeletal hyperostosis spares the sacroiliac joints and preserves disc height. Ankylosing spondylitis shows sacroiliitis, syndesmophytes and squared vertebrae, which are the features that separate the two.

Which symptom of diffuse idiopathic skeletal hyperostosis most often needs surgery?

Dysphagia caused by large anterior cervical osteophytes is the symptom of diffuse idiopathic skeletal hyperostosis most often needing surgical treatment. An unstable fracture of the rigidly ossified spine after minor trauma also requires surgical stabilisation.

How should a fall in diffuse idiopathic skeletal hyperostosis be assessed?

A fall in diffuse idiopathic skeletal hyperostosis should be imaged even when pain seems mild, because the rigid ossified spine fractures easily. Missed fractures can progress to instability or cord injury, so a low threshold for CT is appropriate.

Is diffuse idiopathic skeletal hyperostosis an inflammatory condition?

No, diffuse idiopathic skeletal hyperostosis is a non-inflammatory condition and is not managed as a spondyloarthropathy. Management is symptomatic with NSAIDs and physiotherapy, and surgery is reserved for complications such as dysphagia or fracture.