Swayback
Look up swayback in Wiktionary, the free dictionary.
Swayback, also known clinically as lordosis, refers to abnormally bent postures in the backs of humans and of quadrupeds, especially horses. Extreme lordosis can cause physical damage to the spinal cord and associated ligaments and tendons which can lead to severe pain. In horses, moderate lordosis does not generally impact an animal's usefulness and does not necessarily cause lameness.