This illustration is slightly exaggerated for teaching purposes. It indicates the appalling distortion sustained by a pelvis which has "dropped" on the right side (so common), driven by an unstable sacrum, which is the pelvis's middle component. The spine is now sitting-on an oblique side to side pelvic base, and so the spine contorts accordingly. Even worse when the sacrum "twists" around on an horizontal plane. Perhaps the creator wondrously made us perfect as long as we inherited a "full pack of cards". So many adverse factors intercede during our life-time that imperfections develop. These cause a series of pathological weaknesses: pelvic instability being one of them.