Index
This joint stabilizes the weight of the legs, and the upper body is a fundamental unit for transferring strength between the legs and torso.
The sacroiliac joint is located in the pelvis, between the back of the hip and the sacrum, connecting the iliac bone in the pelvis and the lower part of the spine at the level of the hips, the sacrum.
The sacroiliac joint is strengthened with the support of a network of ligaments and muscles, which likewise restrict movement.
A typical sacroiliac joint has a minimal amount of movement, approximately 2-4 mm of displacement in multiple directions.
The nature of the sacroiliac ligaments in women is less complicated than in men since it requires mobility so that the movement necessary for the birth process can be carried out.
Types
The sacroiliac joint on the front is classified as a diarthrodial joint since this is a type of articulation that can move freely.
It comprises the sacrum and the two hip bones on the back. However, the articulation on the back is not as mobile as on the front.
The bones remain in place due to the ligaments; these ligaments help the sacrum support the spine and head’s weight and ensure the joint’s fit.
The ligaments in the posterior part of the sacroiliac joint are more abundant in the posterior part than in the anterior.
Some of the ligaments on the back are:
The interosseous sacroiliac ligament is arranged between the sacrum and the ilium. This ligament maintains the congruence of the joints and is located at the point where the transfer of the most significant load of weight from the spine to the hip and lower extremities occurs.
The posterior sacroiliac ligament: This ligament is a continuation of the interosseous sacroiliac ligament. It is the one that supports the interlocking mechanism in the frontal planes of the bones (Ilium and sacrum); In this way, it helps the sacrum to support the entire weight of the spine.
The iliolumbar ligament: Supports weight transfer and support functions of the sacroiliac interosseous and posterior sacroiliac ligaments.
The sacrotuberous ligament is a large ligament that goes from the sacrum to the ischial tuberosities.
The sacrospinous ligament: This is a ligament smaller than the previous one with the same disposition, but it does not cover both the joint and the sacrotuberous ligament.
The sacrotuberous and sacrospinous ligaments restrict the bending movement of the sacrum.
characteristics
In the adult, the structure of the sacroiliac joint is oblong, with a concave groove in the back and convex in the anterior, the joint has the shape of an ear or a bean.
The sacroiliac joint has two classifications, one type in the anterior part of the joint and the other in the posterior part.
In the anterior part, it is a synovial or diarthrodial joint. This type of articulation is capable of many movements. The joint is classified as a syndesmosis in the posterior part, which are protective structures against excessive movements.
The external contours of the ilium and the sacrum comprising the sacroiliac joint are connected and interlock to form the anterior part of the joint. The integrity of the sacroiliac joint is maintained only by this interlocking mechanism and the ligaments.
The portions of the gluteus maximus muscles and the piriform muscles cross the sacroiliac joint.
Function
The sacroiliac joint is responsible for supporting the weight of the spine and distributing this weight in the area between the hip and the foot.
It is responsible for transmitting torsional or rotational forces from the lower extremity to the vertebral column.
The sacroiliac joint also transmits the weight of your spine to the ischial tuberosities when the person sits down.
Movements
The front part of the sacroiliac joint is classified as a synovial joint, but it only has a small degree of movement.
However, although it is a synovial joint, movement is limited due to the high level of support of the joint and the compromise of weight transfer, which requires a lot of stability and a close connection between the sacrum and the ilium.
Therefore, the movements of the sacroiliac joint include:
- The movement of the hip bones when they lean forward while the fixed sacrum remains called the anterior innominate inclination.
- The movement of the hip bones when they lean back while the sacrum remains fixed is called innominate posterior inclination.
- The movement of a hip bone when it leans forward, bending the other backward, leaving the sacrum fixed. This movement happens when walking and is called antagonistic inclination.
- When the sacrum flexes, it is called nutation, and when the sacrum is extended, it is called continuation.
Sacroiliac joint dysfunction
Problems of the dysfunctionality of the sacroiliac joint are a common origin of low back pain, with additional symptoms such as pain in the thigh and buttocks that can radiate down the sciatic nerve but rarely radiate to the foot.
