The purpose of this study was to investigate whether transitional vertebrae contribute to the development of sacroiliac joint dysfunction. The prevalence of transitional vertebrae in patients with lumbar pain was determined during this process, and the prevalence of sacroiliac dysfunction was compared between patients with low back pain and healthy volunteers.700 subjects, 500 with low back pain and 200 healthy volunteers were included in this study. Five tests were applied to all participants to determine sacroiliac joint dysfunction. Positivity in three tests was regarded as dysfunction. Lateral lumbosacral and Ferguson angle X-rays were taken from the group with low back pain. The patient was evaluated a specialist radiologist in terms of presence or absence of transitional vertebrae, and if identified, what type.Transitional vertebrae were determined in 26% (n = 130) of the patients with low back pain. Type 1a was determined in 20%, type 1b in 10%, type 2a in 26.9%, type 2b in 30.8%, type 3a in 0.8%, type 3b in 4.6% and type 4 in 6.9%. The prevalence of sacroiliac joint dysfunction in the low back pain group (15.4%) and the prevalence of sacroiliac joint dysfunction in cases of transitional vertebra (28.5%) were significantly higher compared to the control groups (p < 0.05).Sacroiliac joint dysfunction must be considered when investigating the etiology of low back pain. Particular sensitivity must be exhibited on this subject in patients with transitional vertebrae.