istuinluu

Istuinluu, known in Finnish as istuinluu, is one of the three components of the hip bone (os coxae), along with the ilium and pubis. It contributes to the posterior portion of the acetabulum, the socket that forms part of the hip joint. The ischium consists of a body, a ramus (ischial ramus), and the prominent ischial tuberosity. The body helps form the acetabulum, while the ramus joins with the inferior ramus of the pubis to complete the ischiopubic ramus and contribute to the obturator foramen.

The ischial tuberosity is the weight-bearing “sit bone” that bears pressure when a person sits. It serves as an attachment site for several structures, including the hamstring muscles (the long head of the biceps femoris, semitendinosus, and semimembranosus) and the sacrotuberous ligament. The ischial spine, located above the tuberosity, is an important anatomic landmark; it is the attachment point for the sacrospinous ligament and lies near pathways for nerves and vessels such as the pudendal nerve.

Clinical significance includes fractures and avulsions of the ischial tuberosity, which can occur in direct trauma or during vigorous contraction of the hamstrings in athletes. Prolonged sitting can lead to pressure-related issues over the ischial tuberosities, including pressure ulcers in at-risk individuals. In medical procedures and imaging, the ischial spine and tuberosity serve as landmarks in pelvic radiography and surgical approaches, and knowledge of nearby neurovascular structures, such as the pudendal and sciatic nerves, aids in diagnosis and treatment. The ischium fuses with the other pelvic bones in adulthood, and its features are routinely visible on radiographs and CT scans.