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Pelvic girdle joints and ligaments
Other Terms: Ligaments of the pelvic girdle, Pelvis
The pelvic girdle forms joints between the two pubic bones and between the ilia and sacrum. The interpubic joint is a symphysis type of cartilaginous joint. This strong fibrocartilage structure binds the two os coxae and allows for a small range of motion. The sacroiliac joint is a composite joint that has both a syndesmotic junction and a synovial capsule. The syndesmosis occurs where strong anterior and posterior sacroiliac ligaments bind the os coxa to the sacrum. In addition to these sacroiliac ligaments, iliolumbar, sacrospinous, and sacrotuberous ligaments also stabilize the os coxae on the sacrum. The synovial sacroiliac joint occurs where the lateral alar surface of the sacrum articulates with the ear-shaped auricular surface of the ilium. Originally synovial, with age this joint often forms fibrous adhesions and becomes obliterated later in life, sometimes even ossifying. This joint allows for a small degree of anterior-posterior rotation that accompanies flexion and extension of the trunk.