Joint hypermobility and genetic collagen disorders: are they related? If this same question had been posed a quarter of a century ago, the answer would have been very different from what is appropriate today. Conventional wisdom1 has always favoured the view that “common” hypermobility merely represents the upper end of a Gaussian distribution of the “normal” joint range of movement. That view is now challenged by the notion that this variety of hypermobility, at least as far as it is seen from the clinic, may represent a departure from “normality”. The inference is that it is a forme fruste of a genetic connective tissue disease (or heritable disorder of connective tissue (HDCT)). This does not, of course, exclude the possibility that “common” hypermobility, such as is seen in musicians and dancers, may be non-pathogenic polymorphisms, as a result of minor variations in extracellular matrix genes such as collagens, elastin, fibrillins, etc. Other variations might be in different, more interactive regions of the protein and are then pathological.