The pelvis is the structure responsible for connecting the spine to the lower body. The pelvis protects the bladder, intestines, and many important blood vessels. Many of the most important leg muscles and abdominal muscles attach to the pelvis and allow for body and function.
The ischial tuberosity (also referred to as your ‘sit bones’) is a pair of rounded bones that extend from the bottom of the pelvis – they are the bones that we generally sit on daily. Anatomically, the pelvis consists of three strong bones fused together:
- The ilium – The ilium is an essential part of the pelvic girdle. This type of bone serves a weight-bearing function and is part of the structure that ensures the spine is supported when the body is upright.
- The ischium – The ischium is located beneath the ilium and behind the pubis. As part of the hip joint, this bone plays a very important role in leg mobility, balance, standing up and lifting tasks.
- The pubis – Also known as the pubic bone, is the most forward-facing bone of the pelvic bones. Together with the ilium, and ischium, the pubis helps form the deep, cup-shaped structure of the pelvic girdle. The main function of the pubis is to protect the urinary organs (like the bladder or prostate) as well as the internal sex organs.
The ischial tuberosity is also divided into two parts, such as:
- Upper region – The upper region is in the superior (uppermost) position of the bone, having a smooth shape consisting of four angles. It is subdivided into two sections by a ridge running downward and outward.
- Lower region – The lower region of the ischial tuberosity appears as an irregular-shaped triangle situated at an inferior (lowermost) position. It is divided into two parts by a longitudinal ridge running from the base to the top of the structure.
- Pain to the ischial tuberosity can be caused by irritation or injury to the local structures or can be referred to from other structures. Inflammation of the hamstring or adductor tendon can cause tendonitis and may cause pain in your sit bones. Irritation or inflammation of the ischial bursae can cause sit bone pain as well. The bone itself is also vulnerable to injury and fracture of the ischial tuberosity which can cause significant sit bone pain.