The purpose of this paper is to review the anatomy and function of the pelvis in order to enhance the clinical understanding of this closed chain kinematic complex. The relevant bony and soft tissue anatomy is discussed with an emphasis on the complex and unique features of the related parts of the pelvis. Osteokinematics of the pelvis and the sacroiliac joints are discussed relevant to functional movements of the spine and lower extremities. Intrapelvic joint surface motion is presented in light of past and more recent experimental work. Questions regarding the validity of clinical sacroiliac models and future research are posed. J Orthop Sports Phys Ther 1991;13(2):71-84.