One of the most common traits of achondroplasia, apart from the distinctive shorter length of the long limbs and consequently shorter height, is joint hypermobility . Joint hypermobility (also referred to as benign joint hypermobility) means that your joints are looser and more flexible than the average person's. Many may know the term "double jointed" which refers to the same thing. Joint hypermobility is not exclusive to achondroplastics, I for example have it - most kids have it to a certain degree but outgrow it. Kids with achondroplasia tend to be many times more supple than an average height child is though. The photo above is from last summer so our son is 18 months old or so, he can still sit like that with ease (he often draws on the soles of his feet by pulling his leg up like this) and he will continue to be able to do that for a long time to come. He can do the splits with ease and he uses his extreme flexibility to his advantage a l...