Introduction: The Lumbar Spine Instability Questionnaire (LSIQ) is a patient-reported outcome measure (PROM) suggested to measure clinical instability of the spine.

Objective: The aim was to translate and cross-culturally adapt the LSIQ into Swedish and to test its measurement properties.

Methods: We included people with low back pain (LBP) seeking primary care (n = 101). The LSIQ was translated using international recommendations. Construct validity was investigated via the Roland Morris Disability Questionnaire (RM) and the Numeric Pain Rating Scale (NPRS). Reliability was tested via test-retest (Intra Class Correlation, ICC2.1) (n = 50) and by analyzing internal consistency (Cronbach Alpha). A suggested cutoff score was used to study discriminative ability.

Results: The LSIQ was successfully translated into Swedish. For construct validity, a moderate correlation was shown with the RM (rho 0.58) and the NPRS (rho 0.47). Test-retest demonstrated high reliability for the total score (ICC2.1 0.94, 95% CI 0.86–0.96). Internal consistency reached a Cronbach Alpha of 0.64. Participants scoring higher on the LSIQ (≥9) showed significantly higher pain and lower disability levels, were of higher age and less physically active.

Conclusion: The Swedish LSIQ shows acceptable measurement properties regarding test-retest reliability and validity. To further study the usefulness of the LSIQ and the suggested cutoff score, the dimensionality needs to be investigated.