Tuber ischiadicum | Ischium

Tuber ischiadicum

The ischial tuberosity is a prominent bony prominence that forms the lower end of the bony pelvis. It has a rough surface and essentially fulfills two functions. On the one hand, it forms the point of origin for a whole group of muscles of the thigh and buttock, the so-called thigh flexors.

From there, these muscles move over the back of the thigh to below the knee, where they attach to the lower leg bones. They are mainly used for flexion in the knee joint, as well as for extension in the hip, which is crucial for movements such as climbing stairs. On the other hand, the ischial tuberosity serves as a support point when sitting and is overlaid by an extensive fat pad for this purpose.

Function

Due to its anatomical position, the ischium fulfils three main functions. Firstly, as the name suggests, with its large ischial tuberosity, it serves as the deepest point of the bony pelvis and thus as a support point when sitting. On the other hand, with its numerous bone edges and tips, it functions as the point of origin for several muscles of the thigh and the pelvic floor.

Its main task, however, is mainly to stabilize the bony pelvic ring. It fulfills this task on the one hand through its firm connection with the pubic and iliac bone, and on the other hand through its function as a starting point for several ligaments of the sacroiliac-iliac joint. These are very tightly stretched between the bones and thus provide the necessary stability in the pelvis.

Pain in the ischium

Pain in the ischium can have many different causes. These can best be classified according to the group of structures that are affected. On the one hand, processes in the bone itself can be the cause of the pain.

The main causes are fractures caused by falls or accidents, inflammation of the bone tissue and tumors. In adolescents, jerky leg movements or overloading, e.g. by running hurdles, as well as long and high jumps can also lead to so-called apophysiolyses. These are breaks in the ossification centers, which play a decisive role in bone growth.

Another reason for pain in the ischium area can be injuries to the connective or muscle tissue. These are mainly bruises, e.g. from falls, as well as strains and torn muscle fibers due to overstrain. Irritations and inflammations of the muscle tendons at the ischial tuberosity, due to friction of the tendons against the bone, are also common. Inflammations of the muscles themselves are rarer.The os ischii and its adjacent structures form several points of passage for nerves that run from the pelvis to the leg. At these points there can also be irritation and especially entrapment, which can cause severe pain.