The cord is a progressive stage of the nodules often along the path of a tendon. They are usually quite hard, all the time, whereas tendons not under tension are softer. Also cords often attach to the surface skin and do not move as tendons do which appear to slide under the skin, although this can be confusing since cords often follow the paths of tendons.

In the early stage where cords are not so prominent or hard it may take an experienced hand doctor to determine the difference. In later stages when they become rock solid, fixed to the skin, with some contracture, diagnosis is easier, maybe obvious. I think the best comparison is with the other hand, assuming you don't have bi-lateral disease, or a friends hand assuming they don't have the condition either.

Edit to add see this website http://www.dupuytrens.me.uk/dupuytrens.html for a good anatomical view of other structures in the hand that are often associated with DD.

Edited 01/06/15 18:58