Emma was born with arthrogryposis multiplex congenita which a rare birth defect of unknown origin. It is characterized by multiple permanent shortenings of muscles, joints or both.
In Emma's case her legs were able to be casted to "normal" which meant a long process of stretching her legs to their current limits and then putting them in a cast to keep them in place and repeating the process multiple times. However, her arms did not respond to treatment and it was feared she's never be able to lift her hands to her face.
Then her parents found the researchers at Delaware hospital, and thanks to cutting edge technology, were able to help Emma use her magic arms.