Degenerative Spondylolisthesis

Overview

Degenerative spondylolisthesis is a condition in which one vertebral body slips forward relative to the vertebra directly below it, driven by the accumulated effects of aging on the spine rather than a structural defect in the bone. The slip most commonly occurs at the L4–L5 level, where the normally more sagittal orientation of the facet joints and the higher degree of segmental motion create a predisposition to instability. It is several times more common in women than in men (a difference tied in part to hormonal influences on ligament laxity and to differences in pelvic and facet morphology), and it is rarely seen before the fifth decade of life.

As the disc loses height and stiffness over time, facet joint arthrosis, joint-capsule laxity, and ligamentous remodeling allow the upper vertebra to gradually translate forward. Because the neural arch remains intact (unlike in isthmic spondylolisthesis, where the arch has a structural defect), the slip is typically low grade (Meyerding grade I or II). The consequence of that translation, combined with hypertrophy of the facets and ligamentum flavum, is progressive narrowing of the central canal, lateral recesses, and neural foramina, which compresses the nerve roots and drives the clinical syndrome.

What causes it

The underlying process is a cascade of age-related degenerative changes that collectively reduce the structural stability of the lumbar segment. Disc desiccation and loss of disc height reduce the segment's resistance to forward shear forces. Simultaneous arthrosis of the facet joints erodes their ability to block translation, and stretching or laxity of the facet capsules and posterior ligaments allows gradual forward creep of the upper vertebra.

Established risk factors include advancing age, female sex, sagittally oriented facet joints at L4–L5, increased body mass index, prior pregnancy, and generalized ligamentous laxity. Diabetes and other metabolic conditions that accelerate disc degeneration may also contribute to development and progression. The L4–L5 segment is involved in the large majority of cases; L3–L4 and L5–S1 are less frequently affected.

Symptoms and warning signs

Many patients are asymptomatic, with the slip found incidentally on imaging obtained for another reason. When symptoms develop, the most characteristic presentation is neurogenic claudication: bilateral or unilateral buttock, thigh, and leg discomfort, heaviness, or cramping that comes on with standing and walking and is relieved by sitting or bending forward, the so-called shopping-cart sign, which flexes the spine and opens the narrowed canal. Lumbar radiculopathy, most often involving the L5 nerve root at the L4–L5 level, may cause dermatomal leg pain, tingling, or focal weakness. On examination, a palpable step-off at the affected level, hamstring tightness, and reproduction of symptoms with lumbar extension are common findings, though neurologic signs can be subtle.

Certain features demand prompt attention. Saddle anesthesia (numbness in the groin, inner thighs, and perineum), new difficulty controlling the bladder or bowel, or rapidly worsening weakness in both legs are warning signs of cauda equina syndrome, a surgical emergency requiring immediate imaging and decompression. Fever, unexplained weight loss, night pain, and a history of malignancy should prompt evaluation for infection or tumor rather than a degenerative slip. Recent significant trauma warrants assessment for an unstable injury that is separate from a degenerative process.

How it's diagnosed

The diagnosis combines a clinical assessment with targeted imaging. Standing lateral radiographs, taken upright rather than supine, establish the presence and grade of the slip; the vertebra can reduce when the patient lies flat, so supine-only films can underestimate or miss the slip entirely. Flexion-extension lateral views assess whether the slip increases with movement, indicating dynamic instability that has direct implications for surgical planning.

MRI is the preferred modality for characterizing soft-tissue and neural compression. It shows central canal stenosis, lateral recess and foraminal narrowing, facet joint arthrosis and effusions, and which nerve roots are involved. CT or CT myelography is used when MRI is contraindicated or when clearer bony detail is needed, particularly to confirm that the neural arch is intact and to distinguish a degenerative from an isthmic slip.

Because stenosis and slippage are common incidental findings in older adults, imaging must always be interpreted in the context of the patient's symptoms and neurologic examination. Electrodiagnostic studies and selective nerve root blocks can help localize the symptomatic level when clinical and imaging findings point in different directions. Assessment of the hip and sacroiliac joints helps exclude common mimics such as hip osteoarthritis and sacroiliac joint pain.

Treatment options

Most patients are managed without surgery. Conservative care typically begins with activity modification, a structured physical therapy program emphasizing core strengthening and flexion-based exercise to reduce segmental loading, anti-inflammatory medication, and weight management. These measures address both symptoms and the mechanical factors that promote progression.

Epidural steroid injections and selective nerve root blocks can provide meaningful relief and help confirm the symptomatic level, though their benefit is often temporary. They are most useful as a bridge to other treatment rather than a long-term solution.

When surgery is considered

Surgery is considered when neurogenic claudication or radiculopathy remains disabling despite an adequate course of non-operative care (commonly six to twelve weeks or longer), when there is progressive neurologic deficit, or when cauda equina syndrome is present, which requires emergent intervention.

The cornerstone of surgery is decompression to relieve pressure on the compressed nerve roots. Whether to add instrumented fusion is an individualized decision. Fusion is generally favored when flexion-extension imaging demonstrates dynamic instability, when the slip is higher-grade or mobile, when significant low back pain is a dominant symptom, or when decompression alone would risk destabilizing the segment. Well-selected patients who undergo decompression with or without fusion typically achieve meaningful improvement in pain, function, and walking tolerance. As with any spine operation, though, these procedures carry risks, including infection, dural tear, nonunion (pseudarthrosis) or hardware problems when fusion is performed, adjacent-segment degeneration over time, and the possibility of needing a revision procedure. Not everyone improves, and some patients have persistent symptoms afterward. The linked procedure pages discuss these risks in more detail, and your surgeon will weigh them against the expected benefit for your specific situation.