The results of the SIJ hypomobility tests (including the Gillet test, standing flexion and sitting flexion tests) improved significantly in the 5th session and after 1-month follow-up compared to baseline values, whereas no statistically significant improvement was observed in the SLR and slump tests. Spinal manipulative therapy may enhance mobility of the SIJ and lumbar vertebrae, and affect the muscles in these regions, thus accounting for the improvement in pain and functional ability. However, significant changes in the slump and SLR tests may require additional interventions such as soft tissue manipulation and nerve mobilization, which were not tested in this study.