I am a 43 year old woman, and have been hypermobile all my life. Fortunately, apart from easily-twisted ankles and occasional knee pain, I have never had any issues; I've never been officially diagnosed nor would I consider myself to have HMS. One of my daughters and my 8 year old son share my flexibility. While my daughter has not had any problems, my son has a number of issues I am beginning to suspect may be related to his hypermobility. I have an appointment scheduled with a pediatrician but I like to be as informed as possible and thought posting here might help.
My son has had severe leg pain all his life. When he was younger he would frequently wake up in the middle of the night, screaming in pain. Numerous pediatricians told us it was growing pains. It is a little less severe now but I'd say at least a third of the time he complains his legs hurt in the evening. He also fidgets constantly, in particular when he's tired. In fact, "fidget" is probably too benign a word; he literally can't stop moving to the point it is nearly unbearable to be near him sometimes. He also cracks his knuckles and neck.
I never thought too much about any of those things since they didn't seem too out of the ordinary. However, recently, I have noticed that, when my son moves his shoulders and upper back, there is what I can only describe as crunching. It is audible if I am close enough and when I put my hand on his back, I can feel the crackling all through his upper back and shoulders. He says he has brief discomfort when he first raises his shoulders but he has not otherwise complained. When I started looking into possible causes, I kept coming across HMS and since he does in fact have a number of hypermobile joints, I'm wondering if this weird crunching may be related, as I've never seen such a thing before. Any thoughts would be appreciated.

