It is generally believed that radiological signs of lumbar degenerative disc disease (DDD) are associated with increased pain and functional impairment as well as lower health-related quality of life (HRQoL). Our aim was to assess the association of the Modic and Pfirrmann grading scales with established outcome questionnaires and the timed-up-and-go (TUG) test. METHODS: In a prospective two-center study with patients scheduled for lumbar spine surgery, visual analogue scale (VAS) for back and leg pain, Roland-Morris Disability Index, Oswestry Disability Index and HRQoL, as determined by the Short-Form (SF)-12 and the Euro-Qol, were recorded. Functional mobility was measured with the TUG test. Modic type (MOD) and Pfirrmann grade (PFI) of the affected lumbar segment were assessed with preoperative imaging. Uni- and multivariate logistic regression analysis was performed to estimate the effect size of the relationship between clinical and radiological findings. RESULTS: Two hundred eighty-four patients (mean age 58.5, 119 (42 %) females) were enrolled. None of the radiological grading scales were significantly associated with any of the subjective or objective clinical tests. There was a tendency for higher VAS back pain (3.48 vs. 4.14, p = 0.096) and lower SF-12 physical component scale (31.2 vs. 29.4, p = 0.065) in patients with high PFI (4-5) as compared to patients with low PFI (0-3). In the multivariate analysis, patients with MOD changes of the vertebral endplates were 100 % as likely as patients without changes to show an impaired TUG test performance (odds ratio (OR) 1.00, 95 % confidence interval (CI) 0.56-1.80, p = 0.982). Patients with high PFI were 145 % as likely as those with low PFI to show an impaired TUG test performance (OR 1.45, 95 % CI 0.79-2.66, p = 0.230). CONCLUSIONS: There was no association between established outcome questionnaires of symptom severity and two widely used radiological classifications in patients undergoing surgery for lumbar DDD