Pattern 1

One of the body shape characteristics of people suffering from SI joint pain is that the center of the body leans forward, as shown in the 1st image. As detailed in the video below, when the core is weak, the center of the body tends to move forward. This naturally puts the gluteus muscles out of the neutral position. As a result, the hip muscles gradually weaken and tighten. Since they attach near the SI joint (See the 2nd image), tight hip muscles create a force that pulls on the attachment, which makes the joint unstable. This can eventually cause joint pain or you can feel the pain from the gluteus tendons as 'SIJ pain'.

Pattern 2

The second body feature is that the center of the body is shifted to one side, as shown in the 3rd image. In the case of this woman, her weight is shifted to the right, and in this case, her right gluteus medius is likely to lengthen and weaken. The weakening of this side hip muscle makes the whole pelvis unstable (See the 4th image), which can increase friction in SI joint and hence pain.

The left gluteus medius muscle on the other side is also out of the neutral position in this woman's case and is placed in a shorter position. Muscles in a shorter position are slowly tightened over time and tight muscles can't function properly, which will eventually affect the SI joints too. Therefore, whether the muscles are shortened or lengthened, "muscles that are not functioning properly in their neutral position" can cause joint problems.

Pattern 3

Finally, the third physical feature is that the pelvis rotates to one side, as shown in the 5th image. The more severe the pelvis is twisted, the more it turns to one side when you relax your body, In the case of this man, his pelvis turns to the right. Then, the SI joint on the left is positioned slightly in front of the other, so the phenomenon described in pattern 1 is likely to appear.

In addition, his right SJ joint is likely to become unstable as the gluteus medius muscle lengthens/weakens due to his pelvis rotating to the right, as described in Pattern 2) In any case, these body features often appear in combination like patterns 1, 2 or 2, 3 rather than just one, so it is recommended to do exercises that balance the body shape together.