Spondylolisthesis: When a Vertebra Slides Forward

What Is Spondylolisthesis?

Spondylolisthesis is a condition in which one vertebral body slips anteriorly (forward) relative to the vertebra immediately below. The term derives from the Greek spondylos (vertebra) and olisthesis (to slip). It most commonly occurs at the L4-L5 and L5-S1 spinal segments — the levels subject to the greatest mechanical loading in the lumbar spine — though it can occur at any spinal level. The degree of slip is classified using the Meyerding grading system: grade I (0–25% slip), grade II (25–50%), grade III (50–75%), grade IV (75–100%), and grade V or spondyloptosis (greater than 100%, where the vertebra slips completely off the one below).

Types of Spondylolisthesis

Isthmic spondylolisthesis is the most common type in younger patients. It results from a defect or stress fracture in the pars interarticularis — the narrow bridge of bone connecting the superior and inferior articular processes of the vertebra. When this bony bridge fractures on both sides, the vertebral body loses its posterior anchor and is free to slip forward. Pars defects (spondylolysis) are found in up to six percent of the general population and are particularly prevalent in adolescent athletes performing repetitive lumbar hyperextension — gymnasts, fast bowlers in cricket, and weightlifters.

Degenerative spondylolisthesis is the most common type in adults over 40. It occurs without a pars defect; instead, progressive facet joint degeneration and disc height loss reduce the mechanical stability that normally resists forward shear, allowing the vertebra to translate anteriorly. L4 slipping on L5 is the classic presentation. Dysplastic spondylolisthesis is congenital, arising from developmental insufficiency of the posterior elements. Traumatic and pathological types are less common, resulting from acute fractures or bone disease respectively.

Symptoms and Clinical Presentation

Many individuals with spondylolisthesis — particularly low-grade isthmic cases — are entirely asymptomatic and discovered incidentally on imaging performed for another purpose. When symptomatic, the most common presentation is central or bilateral lower back pain that is aggravated by lumbar extension and prolonged standing. If the slipped vertebra narrows the neural foramina or compresses the nerve roots, radicular symptoms — pain, tingling, or weakness radiating into the buttock and leg — may develop. Degenerative spondylolisthesis at L4-L5 frequently produces neurogenic claudication — leg pain and heaviness during walking that is relieved by sitting or forward lumbar flexion — through its contribution to lumbar spinal stenosis.

Conservative and Surgical Management

The vast majority of spondylolisthesis cases — including most grade I and II presentations — respond well to conservative management. Pain neuroscience education and reassurance that movement is safe are foundational, as many patients become unnecessarily fearful of activity after a spondylolisthesis diagnosis. Lumbopelvic stabilisation training — reactivating deep multifidus, transversus abdominis, and pelvic floor — addresses the neuromuscular deficit that contributes to segmental instability. Progressive loading into functional movement patterns (hip hinging, squatting, carrying) is introduced as neuromuscular control improves. Flexion-biased activity modification — temporarily reducing provocative extension loading during acute phases — reduces pain while rehabilitation progresses.

For high-grade slips, neurologically compromised presentations, or conservative management failure after a thorough period (typically six months), surgical consultation is appropriate. Spinal fusion at the affected level stabilises the segment and decompresses neural structures. Outcomes following surgery are generally favourable for carefully selected patients.