Are you double jointed? If not, you probably know someone who is, because this relatively common condition occurs in 10-25% of the population! Technically, the term for ‘having super flexible joints that made you popular on the playground as a kid’ Is hypermobility, and it’s characterized by having shallow joints and flexible ligaments or cartilage. In the vast majority of people, having hypermobile joints is not dangerous, except if they use them to scare other kids.
However, in a minority of hypermobile people, symptoms beyond just increased flexibility can develop, such as joint pain, increased rates of fractures or sprains, fatigue or an increased susceptibility to conditions like whiplash. In cases where symptoms like these do occur, the person is said to have Joint Hypermobility Syndrome. Another condition however can lead to symptoms almost indistinguishable from Joint Hypermobility Syndrome, something called Ehlers-Danlos Syndrome (EDS).
EDS is caused by a genetic mutation that causes defects in either the structure or processing of collagen (the main structural protein of our bodies, making up 25-35% of all proteins) or other proteins that interact with collagen in connective tissue. EDS affects roughly 1 in every 5000 people and can cause less serious effects like chronic pain and easy bruising, or more serious effects like osteoarthritis or aortic dissections (when blood pools between layers of the aortic wall). EDS exists in a few different forms (7 actually), with the hypermobility form affecting approximately 1 in every 10 000 people. This hypermobility form of EDS is functionally undifferentiable from Joint Hypermobility Syndrome. Both conditions have the same diagnosis criteria, and treatment recommendations, and not even a genetic test can identify which syndrome a patient has. Due to this conflation, most experts currently recommend thinking of Joint Hypermobility Syndrome and hypermobility EDS as 1 condition, until a way to distinguish them can be found.