laxity means basically the same as loose. Have you had shoulder dislocations or trauma associated with your shoulders? If looking in the mirror, standing straight with your head straight, and shoulders relaxed(but not to the point of slouching), are there any noticeable difference between the two shoulders? Does one seem to set higher in the socket than the other? Does one seem rolled forward in the joint more than the other? Do you feel like your arms "dangle", like your shoulder feels as if it is no longer in the socket but instead it hangs down in your arm pit some? This is called subluxation. Unless congenital, it is laxity which is usually the result of damage from dislocation or surgery. There are major arteries/nerves that run through the armpit & a subluxed shoulder puts pressure on them which would explain trouble with your arms and will also cause neck problems. Do you have what feels like knots around your shoulder blades and when you notice them all other symptoms seem to be at there worst? Let me know.