Background Pregnancy-related pain may be associated with sacroiliac joint (SIJ) changes, detectable by magnetic resonance imaging (MRI). Purpose To analyze the prevalence and course of SIJ MRI and clinical findings in women referred with low back pain and relate these to pregnancy. Material and Methods A retrospective follow-up study from a longitudinally collected cohort comprising 328 women. Results Women reporting debut of pain in relation to a pregnancy (PP group) tended to have a higher baseline prevalence of all investigated MRI findings, cumulated positive SIJ tests, and a potential fulfilment of the spondyloarthritis diagnosis compared to remainders. The prevalence of subchondral bone marrow edema (BME), any SIJ MRI finding, and potential fulfilment of the spondyloarthritis diagnosis were significantly higher in the PP group compared to women who had not been pregnant. In the total study group, the prevalence of ≥1 MRI finding increased over the four-year study period from 34% to 47% ( P<0.001), driven by increasing prevalence of BME (25% to 32%; P=0.008) and fatty marrow deposition (FMD) (20% to 25%; P=0.020). In addition, the BME volume score increased. Over time, the PP group had persisting high prevalence of buttock pain and total MRI findings and their FMD volume score increased, but there were no between-group differences in MRI variables at follow-up. Conclusion Overall, the prevalence of MRI findings increased over time. Although the PP group had different clinical and SIJ MRI characteristics cross-sectional at baseline compared to remainders, longitudinal analyses revealed that these diminished over time.
What Level of Inflammation Leads to Structural Damage in the Sacroiliac Joints? A Four‐Year Magnetic Resonance Imaging Follow‐Up Study of Low Back Pain Patients