Ischial Tuberosity

The ischial tuberosity is a large bony prominence on the posterior and inferior part of the ischium, one of the three bones that form each hip bone. It projects from the lower rear portion of the pelvis and provides an important attachment site for muscles and ligaments .¹

Several muscles of the posterior thigh originate from the ischial tuberosity. These include the semitendinosus, semimembranosus, and long head of the biceps femoris, which together form much of the hamstring muscle group. Part of the adductor magnus also arises from this region. The sacrotuberous ligament also attaches to the ischial tuberosity .^1,2

The ischial tuberosities also form important load-bearing regions of the pelvis during sitting. Body weight transmitted through the pelvis can produce substantial pressure in the tissues overlying these bony prominences, which is why they are sometimes informally called the “sitting bones” .¹

The ischial tuberosity should not be confused with the ischial spine. Both are projections of the ischium, but the ischial spine is a smaller, pointed projection located higher on the posterior border. The ischial tuberosity is the larger, more inferior prominence and serves as a major attachment site for the hamstring muscles .¹