What To Know About Baastrup’s Sign (Kissing Spine) and Back Pain

Several things can cause back pain, but the usual culprits often involve your intervertebral discs and/or facet joints. However, back and neck pain can be caused by other, less obvious spinal structures.

Baastrup’s sign is known by other names, including Baastrup’s syndrome, Baastrup’s disease, kissing spine syndrome or interspinous bursitis.

What Is Baastrup’s Sign?

Baastrup’s sign is named after Christian Ingerslev Baastrup, who first described the condition in 1933. In Baastrup’s syndrome, pain and inflammation are triggered when the spinous processes of two adjacent vertebrae touch each other—this is how the disorder earned the nickname "kissing spine."

A spinous process is the thin, bony projection that extends off the back of each vertebrae. If you run your hand down your back, you can feel the spinous processes.

Baastrup’s sign most commonly occurs in the lumbar spine (low back), with the L4-L5 segment being the top site. Though rare, you can also develop kissing spine in your cervical spine (neck).

Researchers don’t know how many people have Baastrup’s syndrome, but they do believe it’s relatively common—especially in elderly individuals. Some medical literature has noted that its incidence is as high as 81% in people older than 80.

While the exact cause is not known, kissing spine is associated with degenerative changes in the spine, many of which are caused by the natural process of aging. Baastrup’s syndrome may be caused by disc degeneration—as the discs wear down, it can cause the adjacent spinous processes to meet. As the spinous processes continue to wear down by encountering each other, it can also trigger degeneration elsewhere in the back or neck. That’s why Baastrup’s syndrome is linked to other degenerative spinal conditions, including degenerative disc disease, spondylolisthesis, spondylosis (spinal osteoarthritis), and spinal stenosis.

Though older adults are at a heightened risk for Baastrup’s disease, younger people can also develop it. Athletes who frequently bend and flex their spines—such as gymnasts or football players—may be at risk for kissing spine.

Other possible causes of Baastrup’s syndrome include conditions that may lead to excessive lordosis, including:

• Spinal injury or trauma

• Poor posture

• Scoliosis

• Obesity

What Are The Symptoms of Kissing Spine?

The most common symptom of Baastrup’s syndrome in the lumbar spine is low back pain that worsens when you arch your back (extension) and feels better when you round your back (flexion). The pain also spikes whenever the affected area is touched.

In rare cases when kissing spine affects the cervical spine, you may feel these symptoms in your neck.

As kissing spine can trigger additional degenerative changes in the spine, you may feel symptoms of those secondary disorders. For example, if you develop spinal stenosis in your lumbar spine, you may experience neurologic symptoms, such as radiating leg pain, numbness, and weakness.

How Is Baastrup’s Syndrome Diagnosed?

Though Baastrup’s sign is frequently underdiagnosed because it is mistaken for other more widely understood degenerative spinal disorders, doctors have several diagnostic tools to help confirm the presence of kissing spine.

Your doctor may start your evaluation by performing a physical exam. In addition to gathering your medical history and reviewing your symptoms, he or she may ask you to perform physical maneuvers to recreate the pain you’ve described. Because the pain of Baastrup’s syndrome is aggravated by extension and eased by flexion, your doctor may ask you to arch and round your back to determine how those movements influence your pain levels.

Your doctor will not be able to confirm a kissing spine diagnosis on a physical exam alone—he or she will also need to order imaging scans. Several imaging tests may be used, including X-ray, computed tomography (CT), and magnetic resonance imaging (MRI).

X-ray may show the spinous processes making contact, but CT scans will better illuminate degenerative changes (such as a herniated disc) caused by the disorder. However, MRI is best suited to highlight areas of degeneration involving the soft tissues of the spine and can detect kissing spine in its earliest onset. Your doctor may order a combination of imaging scans to get a complete picture of the affected area.

What Treatments Are Available For Baastrup’s Syndrome?

Back pain associated with Baastrup’s syndrome may be managed with a variety of non-surgical therapies. In some cases, spine surgery may be recommended.

Non-surgical treatments include:

• Steroid injections: To reduce pain and inflammation at the affected area.

• Physical therapy: To stretch and strengthen your core, hips, and spine, and reduce excessive inward curve of the spine (lordosis).

Patients often find success using non-surgical therapies to sustainably manage their back pain, so spine surgery is typically not considered a first-line treatment—that is, you will need to try non-surgical therapies first.

If you are a candidate for spine surgery, your surgeon bases his or her recommendation on the cause of kissing spine and your symptoms. Surgical procedures may include:

• Osteotomy: A wedge-shaped cut into bone to correct alignment.

• Partial or total removal of an affected spinous process.

• Interspinous process decompression: Implantation of an interspinous device; usually a minimally invasive surgical option.

Could Your Back Pain Be Caused By Baastrup’s Syndrome?

If you’re experiencing symptoms of kissing spine, talk to your doctor about whether this condition could be to blame. A clinical exam and imaging scans may reveal the cause, so you can start treatment that eases your pain and restores your function.