Ok, I'm about to get really chewed up for this, but they are cute. You can't deny that. That does not mean people should go around breeding them. They are, in every since of the word, freaks of nature. Because of this, they have health problems, etc, etc. Everyone else who has already posted on this tread has already covered this is detail.
You wouldn't find a miniature dwarf walking using the outside of its ankles instead of a firm solid hoof cute. I watched a miniature horse have joints in her front end so loose, she got around my walking on the outside of her ankles. Her front legs were completely deformed.
She had an under bite so huge she couldn't eat.
Some common phenotypic characteristics of Dwarfism in the Miniature Horse Breed:
1. Achondroplasia—(legs do not grow in length). Normal bone growth does not occur and often develops unevenly at the joints, causing crooked legs.
2. Dwarf foals are sometimes born with contracted tendons or tendon laxity. Joint enlargements and joint deviations are common, often becoming progressively serious with age. Extreme cow hocks, extremely short gaskins and sever sickle hocks all with varying degree of joint laxity and /or joint weakness are also common. Premature Arthritis is common as well.
3. Some types of dwarfs have an over bite, or an under bite. If an undershot jaw is present, the molars may also be out of alignment, requiring that the teeth be floated more frequently than for a horse with a normal mouth. Highly placed nostrils always accompany the undershot jaw.
4. Brachycephalic dwarfs have a large buldging forehead with an extreme dished face, overly large eyes (sometimes placed at uneven angles) and nostrils placed too high up on the face. A second type of dwarf has a more normally shaped head and eye and longer neck, but its head and body are still oversized when compared to the length of its legs. This second type of dwarf does not usually have an undershot jaw.
5. Head obviously longer than the neck. In some dystrophic dwarfs, the neck appears to come directly out of the shoulders.
6. Girth depth is greater than the leg length. Disproportionately oversized entrails and genitals. That is why so many dwarfs have the big “pot bellies.” 7. Vertebra deviations are common.
8. Often unable to rear or stand on hind legs. Some types have an odd “tilting backward” gait with shoulder higher than the croup. 9. Sometimes associated with the various dwarfism syndromes are less obvious characteristics such as mental ******ation, heart and other internal organ defects, sterility, shortened life span, arthritis and inactivity or depression (both of which are probably due to pain).