With such hyper-extensibility, it is also quite common (if not the norm) to find the muscles surrounding the joints to be a major source of compensation when such instability exists. Excessive lordotic curvature – lumbar hyperlordosis, is also called "hollow back", and "saddle back" (after a similar condition that affects some horses); swayback usually refers to a nearly opposite postural misalignment that can initially look quite similar. Common causes of lumbar hyperlordosis include tight low back muscles, excessive visceral fat, and pregnancy. Rickets, a vitamin D deficiency in children, can cause lumbar hyperlordosis. Lumbar hypolordosis
Being less common than lumbar hyperlordosis, hypolordosis (also known as flatback) occurs when theres less of a curve in the lower back or a flattening of the lower back. This occurs because the vertebrae are oriented toward the back of the spine, stretching the disc towards the back and compressing it in the front. This can cause a narrowing of the opening for the nerves, potentially pinching them.
Weak psoas (short for iliopsoas-muscle that controls the hip flexor) force the dancer to lift from strength of their back instead of from the hip when lifting their leg into arabesque or attitude. This causes great stress and risk of injury, especially because the dancer will have to compensate to obtain the positions required. Muscles – One of the greatest contributors is uneven muscles. Because all muscles have a muscle that works in opposition to it, it is imperative that to keep all muscles protected, the opposite muscle is not stronger than the muscle at risk. In the situation of lumbar lordosis, abdominal muscles are weaker than the muscles in the lumbar spine and the hamstring muscles. The muscular imbalance results in pulling down the pelvis in the front of the body, creating the swayback in the spine. Growth spurt – Younger dancers are more at risk for development of lumbar hyperlordosis because the lumbar fascia and hamstrings tighten when a child starts to experience a growth spurt into adolescence.Technical factors

Improper lifts – When male dancers are performing dance lifts with another dancer they are extremely prone to lift in the incorrect posture, pushing their arms up to lift the other dancer, while letting their core and spine curve which is easy to then hyperlordosis in a dancers back. Overuse – Over 45% of anatomical sites of injury in dancers are in the lower back. This can be attributed to the strains of repetitive dance training which may lead to minor trauma.