About iliolumbar ligament, which of the following statements is false (2018)

iliolumbar ligament is a strong, triangular ligament, extending from the thick transverse process of the fifth lumbar veebra to the posterior pa of the inner lip of the iliac crest. It is continuous with the middle and anterior layers of the thoracolumbar fascia and gives paial origin to the quadratus lumborum. It is covered anteriorly by the psoas, and posteriorly by the erector spinae. It prevents anteroinferior slipping of the fifth lumbar veebra under the influence of body weight, and also prevents forwards movement at the sacroiliac joint. sacrospinous ligament bind the sacrum to the ischium. Ref:- BD chaurasia volume 2, pg num:-396,397