Baastrup disease or kissing spine: midline extension pain and imaging
Baastrup disease describes painful contact or close approximation between adjacent spinous processes, usually in the lower lumbar spine. The imaging sign is common in older adults and becomes clinically relevant only when it matches focal midline pain and extension sensitivity.
Repeated extension and loss of disc height may bring adjacent spinous processes into contact. The interspinous ligament and bursa can become inflamed, the opposing bony surfaces may flatten and sclerose, and fluid-filled interspinous or dorsal epidural cysts may develop. Baastrup changes often coexist with disc degeneration, facet arthritis, spondylolisthesis and stenosis, making symptom attribution difficult.
Assessment and differential diagnosis
The examination looks for precise midline tenderness, pain with lumbar extension and relief with flexion. These findings are not specific and should be compared with facet, disc, sacroiliac and stenotic patterns. Lateral radiographs and CT demonstrate close approximation, sclerosis, flattening and enlarged spinous processes. MRI shows interspinous fluid, marrow oedema, soft-tissue inflammation and associated epidural cysts or stenosis. Flexion–extension radiographs may be useful if instability or dynamic separation is clinically relevant.
| Clinical pattern | Possible next step | Why it matters |
|---|---|---|
| Incidental spinous-process contact without matching pain | No Baastrup-specific treatment | The radiographic sign is common and may be asymptomatic. |
| Focal midline extension pain with interspinous inflammation | Conservative care and diagnostic review | The clinical and imaging pattern is more concordant. |
| Temporary relief after targeted interspinous injection | Baastrup pain becomes more plausible | The response supports but does not absolutely prove the pain source. |
| Claudication or neurological deficit with dorsal epidural cyst or stenosis | Stenosis pathway and possible surgery | The neural compression becomes the priority. |
Treatment and decision-making
Initial care may include education, temporary reduction of painful extension, hip and trunk rehabilitation, activity modification and medication after risk review. A fluoroscopy- or ultrasound-guided interspinous injection may be used diagnostically and therapeutically in selected cases. Radiofrequency approaches and surgical resection of the interspinous bursa or part of the spinous process have been described, but evidence is limited. When epidural cysts, stenosis or instability are present, treatment should address the complete degenerative segment rather than the interspinous contact alone.
How to interpret the condition in practice
The term “kissing spines” can sound more dramatic than the clinical situation. The key is to determine whether the interspinous region is truly the dominant pain generator or only one component of broader degeneration.
Locate the tenderness
Pain should be reproducible at the involved midline level.
Compare flexion and extension
The mechanical response can support the hypothesis.
Review the whole segment
Discs, facets, instability and stenosis may be more important.
Use injection cautiously
Temporary anaesthetic relief is supportive rather than definitive.
Track walking and nerves
Neurological symptoms indicate a different treatment priority.
Avoid treating the X-ray alone
The imaging finding may be incidental.
How to monitor the condition and avoid interpretation errors
A credible plan should define what improvement means before treatment begins and should explain how the diagnosis will be reconsidered if the expected response does not occur. Pain intensity can change independently from neurological function, walking tolerance, sleep or participation. For uncommon conditions, progression and safety are often more important than day-to-day symptom fluctuation.
Create a baseline
Record symptom distribution, strength, sensation, walking, sleep, medication use and the activities that matter most.
Use a planned review point
Decide when the response will be reviewed rather than continuing automatically until a treatment package is completed.
Separate relief from diagnosis
Temporary improvement after medication, injection, manual care or a device does not prove the proposed structure was the true cause.
Watch the neurological trajectory
New weakness, spreading numbness, gait change or autonomic symptoms matter even if pain decreases.
Review alternative causes
Degenerative, inflammatory, infectious, oncological and postoperative mechanisms may overlap.
Escalate proportionately
Imaging, specialist referral or surgery should be considered when the risk or functional loss justifies it.
Common errors to avoid
- Treating the most unusual imaging finding instead of the clinically relevant lesion.
- Assuming that a stable imaging abnormality explains a changing symptom pattern.
- Using one negative test to exclude a condition that remains clinically plausible.
- Repeating passive treatment despite no measurable functional progress.
- Generalizing results from a small specialist series to every person with the same label.
- Delaying urgent assessment to complete a predetermined number of visits.
Shared decision-making is strongest when uncertainty is stated directly. A provider should explain what is confirmed, what remains probable, which alternatives still matter and what findings would change the plan. For rare or controversial diagnoses, a second opinion from a clinician experienced with the specific condition may be more useful than adding another non-specific treatment.
Questions before choosing care
What is the leading diagnosis?
Ask which symptoms and examination findings support it.
What alternative remains possible?
Common competing causes should be reviewed before an invasive procedure.
What test changes management?
Avoid testing or imaging that cannot alter the next step.
What outcome matters?
Track function, neurological safety and meaningful activity.
A single symptom, image or treatment response rarely establishes the complete cause by itself.
Relevant specialized resources
Some resources may share ownership or editorial direction; this relationship is disclosed and the links are included for contextual relevance.
Clinique TAGMED
Clinical information about selected mechanical low-back-pain care.
Frequently asked questions
Is Baastrup disease the same as spinal stenosis?
No, although the conditions may coexist.
Why is it called kissing spine?
Adjacent spinous processes come into close contact.
Does every imaging finding cause pain?
No.
Which level is most often involved?
L4–L5 is frequently reported.
Can posture affect symptoms?
Extension often aggravates and flexion may relieve pain.
Can an injection confirm the source?
It can increase confidence but is not definitive.
Can exercise help?
A targeted rehabilitation program may improve tolerance and mechanics.
Is surgery common?
No.
Can a dorsal epidural cyst develop?
Yes, as part of the interspinous degenerative continuum.
Does The Spine Page diagnose Baastrup disease?
No.
Sources consulted
- Rossi et al. — Epidemiology, diagnosis and management of Baastrup disease
- Filippiadis et al. — Baastrup disease pictorial review
- Hatgis et al. — Baastrup disease, bursitis and dorsal epidural cysts
Last editorial review: July 2026. General educational information only.
Dr. Sylvain Desforges, B.Sc., D.O., N.D., osteopath — The Spine Page
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