Background <p>Lumbar disc degeneration and osteoporosis are common degenerative diseases in middle-aged and elderly populations. Although these conditions may be closely related pathophysiologically, their exact comorbidity relationship and underlying mechanisms remain unclear. This study aimed to use imaging indicators to systematically investigate the association between vertebral body bone quality and cranial/caudal endplate bone quality, as well as the severity of lumbar disc degeneration, and to explore the potential clinical value of combined CT–MRI assessment for risk stratification.</p> Methods <p>This was a retrospective study including 2018 patients (8072 intervertebral discs and 10,090 vertebral bodies) who underwent both lumbar CT and MRI at our hospital between September 2023 and June 2025. Data collected included age, sex, body mass index (BMI), smoking status, computed tomography (CT)-based vertebral body and endplate attenuation values (Hounsfield Units, HU), magnetic resonance imaging (MRI)-based cranial and caudal Endplate Bone Quality (EBQ) scores, and the degree of disc degeneration assessed according to the Pfirrmann grading system. Patients were divided into mild-to-moderate and severe degeneration groups based on the mean Pfirrmann grade. To comprehensively evaluate the association of various variables with disc degeneration grades, independent-samples t tests, chi-square tests, scatter plots with fitted linear regression lines, and Spearman correlation analyses were performed. Finally, a binary logistic regression model was used to identify independent risk factors.</p> Results <p>Univariate analysis showed that the severity of disc degeneration was significantly associated with sex, age, average vertebral body CT attenuation, and endplate bone quality (<i>P</i> &lt; 0.05). Binary logistic regression further confirmed that female sex (OR = 1.68), advanced age (OR = 1.093), low average vertebral body CT attenuation value (OR = 0.988), and high cranial EBQ score (OR = 1.235) were independently associated with severe disc degeneration. Further subgroup analysis revealed that the correlation between decreased bone quality and degeneration was more pronounced in female patients. Additionally, segmental analysis indicated that the risk factors for degeneration differed across lumbar spine segments.</p> Conclusion <p>This study found that decreased bone quality of the lumbar vertebral bodies and endplates was significantly associated with the severity of disc degeneration, suggesting a comorbid association between bone quality impairment and disc degeneration, which appeared more pronounced in female patients. Therefore, in clinical practice, the combined assessment of CT-based bone attenuation (HU) and MRI-based endplate bone quality (EBQ) may help identify individuals at high risk for lumbar degenerative diseases and support earlier targeted prevention and management.</p>