Sacroiliac refers to the joint located between the sacrum and the ilium bones of the pelvis. There are several synonyms for this word, including SI joint, sacroiliitis, sacroiliac dysfunction, and pelvic joint dysfunction. SI joint is commonly used by medical professionals to refer to the joint, while sacroiliitis specifically refers to inflammation within the joint. Sacroiliac dysfunction and pelvic joint dysfunction are broader terms that encompass any sort of problem or pain within the joint. Regardless of the specific synonym used, issues with the sacroiliac joint can cause discomfort and mobility issues, and may require medical treatment.