Facet joint dilatation as a radiological indicator of vertebral segmental microinstability

Background: Chronic low back pain (LBP) is a major healthcare burden that reduces quality of life and productivity. Vertebral segmental microinstability is considered a contributing factor in LBP, while radiological signs reflecting biomechanical dysfunction, including disc degeneration, Modic changes, muscle fatty infiltration, and facet joint (FJ) dilatation, remain insufficiently defined as clinical markers. Methods: This was a retrospective cohort study involving 168 adults with chronic LBP. Patients underwent clinical examination including passive lumbar extension (PLE), supine–sit, iliopsoas and quadratus muscle tests, along with lumbar spine magnetic resonance imaging. Imaging findings assessment included rating of FJ dilatation (grades 0–2), Modic changes (grades 0–2), disc degeneration (grades 1–5), and muscle fatty infiltration (grades 0–3). Pain intensity was measured using a 0–10 Visual Analog Scale. Results: Among 168 patients, 70.5% ( n = 120) demonstrated some degree of FJ dilatation, while 16.7% ( n = 28) had high-grade dilatation. Dilatation was significantly associated with Modic type 1 changes, grade 4/5 disc degeneration, muscle fatty infiltration grade 2/3, positive PLE test, and FJ asymmetry. Three factors that did not significantly impact FJ dilatation included disc protrusion, supine-sit test, and muscle dysfunction test. Conclusion: For patients with chronic LBP, FJ dilatation is significantly associated with vertebral degeneration and clinical indicators of lumbar microinstability.