Hypermobility Spectrum Disorder is a term used to describe overly mobile joints which occurs as a result of the protein collagen being more flexible than usual. Hypermobility severity varies. Very severe cases like Ehlers Danlos Syndrome and Marfans Syndrome come with serious complications. However, most people with hypermobile joints do not have any problems. In fact, joint hypermobility can be an advantage in certain sports like athletics, dancing and gymnastics.