Retrolisthesis of C5 on C6 means the fifth cervical vertebra in your neck has slipped backward relative to the sixth vertebra below it. A slip of more than 2 mm on a lateral X-ray is generally considered significant. This is a relatively common finding on neck imaging, most often caused by age-related wear on the discs and joints of the spine, and it ranges from a minor incidental finding to a source of real pain and neurological symptoms depending on severity.
What Happens in the Spine
Your cervical spine is a stack of seven vertebrae separated by cushioning discs and connected by small paired joints called facet joints. The C5-C6 level sits roughly in the middle of your neck and is one of the most mobile segments, which also makes it one of the most vulnerable to wear and tear. In retrolisthesis, the upper vertebra (C5) shifts toward the back of your body relative to C6. This is the opposite of anterolisthesis, where the vertebra slides forward.
The backward slip narrows the space available for the spinal cord and the nerve roots that branch out at that level. Because C5-C6 is responsible for sending nerves into the shoulders, upper arms, and parts of the hands, even a small amount of slippage can cause symptoms if it pinches those structures.
Why It Happens
Trauma and degeneration are the two most common causes of cervical retrolisthesis. In most adults, the process starts with disc degeneration: the rubbery disc between C5 and C6 loses water content and height over time, which reduces the support it provides to the vertebra above. As the disc thins, the facet joints at the back of the spine bear more load than they were designed for. That extra stress leads to facet joint arthrosis, a form of arthritis that erodes the cartilage and loosens the joint capsule. Together, a thinner disc and worn facet joints allow C5 to drift backward.
Acute injuries, such as whiplash from a car accident or a fall, can also force the vertebra out of alignment. In younger people without significant disc degeneration, trauma is the more likely explanation. Less commonly, retrolisthesis results from congenital abnormalities in spine development or from conditions that weaken bone, though these causes are rare at the C5-C6 level.
Symptoms You Might Notice
Many people with mild retrolisthesis have no symptoms at all, and the finding only shows up incidentally on imaging done for another reason. When symptoms do develop, they typically include neck pain, stiffness, and a noticeable loss of range of motion, particularly when turning or tilting your head.
If the slippage compresses a nerve root, you may experience cervical radiculopathy: pain that radiates from the neck into the shoulder and down the arm, along with numbness, tingling, or weakness in the hands and fingers. Headaches originating from the base of the skull are also common. Some people describe muscle fatigue in the shoulders and upper arms that makes it hard to hold objects or lift things overhead.
How It Is Graded
Doctors measure the degree of slippage using the Meyerding classification, which expresses the displacement as a percentage of the vertebral body’s depth. Grade I is a slip of up to 25%, Grade II is 25% to 50%, Grade III is 50% to 75%, and Grade IV is 75% to 100%. Anything beyond 100% is Grade V. Grades I and II are considered low-grade slips and account for the vast majority of retrolisthesis cases in the cervical spine. High-grade slips (Grade III and above) are uncommon in the neck.
On a standing lateral X-ray, the threshold for diagnosing retrolisthesis is typically a backward slip of more than 2 mm. If the vertebra moves 1 mm or more when you flex and extend your neck during dynamic X-rays, that additional motion is considered a sign of segmental instability, which can influence treatment decisions.
How It Is Diagnosed
A standard lateral X-ray of the cervical spine taken while you’re standing is the primary tool for identifying retrolisthesis. The radiologist measures the offset between the back edges of C5 and C6 to quantify the slip. Flexion-extension X-rays, where you bend your neck forward and backward while images are taken, help determine whether the slip is fixed or unstable.
CT scans provide more detailed images of the bone and are useful for measuring the exact degree of slippage and evaluating facet joint damage. MRI is the best tool for assessing soft tissue: it shows the condition of the disc, the degree of spinal cord compression, and whether nerve roots are being pinched. If your imaging report mentions retrolisthesis at C5-C6, your doctor will likely correlate the imaging findings with your physical symptoms before deciding on a course of action.
Treatment Without Surgery
Most cases of C5-C6 retrolisthesis are managed conservatively, especially at lower grades. The goals are to reduce pain, strengthen the muscles that support the cervical spine, and prevent the slip from worsening. Physical therapy is the cornerstone: exercises that target the deep neck flexors and the muscles along the back of the neck help stabilize the segment. Isometric holds, chin tucks, and controlled range-of-motion work are common starting points. A therapist will typically progress you gradually, focusing on endurance and postural control rather than heavy resistance.
Anti-inflammatory medications can help during flare-ups, and some people benefit from short-term use of a soft cervical collar to rest the neck during acute pain episodes. Ergonomic adjustments matter too. If you work at a desk, positioning your monitor at eye level so you aren’t looking down reduces the load on C5-C6. Sleeping with a contoured cervical pillow that supports the natural curve of your neck can minimize strain overnight. Avoid sleeping on your stomach, which forces the neck into extreme rotation.
When Surgery Becomes Necessary
Surgery is reserved for cases where conservative treatment fails to relieve symptoms after several months, or where there are signs of spinal cord compression. The concern with progressive retrolisthesis is the development of cervical myelopathy, a condition where sustained pressure on the spinal cord causes damage that may become permanent. Warning signs include difficulty with fine motor tasks like buttoning a shirt, an unsteady gait, a feeling of heaviness or clumsiness in the legs, and in advanced cases, bowel or bladder dysfunction.
Left untreated, cervical myelopathy can lead to severe pain, nerve damage, difficulty walking, limited use of the hands and arms, and in rare cases, paralysis. Surgical options for cervical retrolisthesis typically involve decompressing the spinal cord or nerve roots and fusing the C5-C6 segment to prevent further movement. The specific approach depends on whether the compression is coming from the front or back of the spine and how many levels are involved.
What to Expect Over Time
Retrolisthesis at C5-C6 is often a slowly progressive condition tied to ongoing disc and joint degeneration. A Grade I slip discovered in your 50s may stay stable for years with good neck muscle strength and posture habits. Periodic imaging, usually every 12 to 24 months, helps track whether the slip is advancing. The single most important factor in long-term outcomes is whether the spinal cord or nerve roots are being compressed. A measurable slip with no neurological involvement carries a much better prognosis than a smaller slip in a naturally narrow spinal canal where even minor displacement crowds the cord.
Staying active, maintaining a healthy weight, and consistently performing neck-strengthening exercises are the most effective ways to slow progression and manage symptoms. Smoking accelerates disc degeneration and impairs healing, so quitting has a direct benefit for spinal health.