I would - yes - if anything happened when you were travelling (and maybe you couldn't have more pain relief because you'd already taken the max yourself), it could be defined as non-disclosure.
I used Endsleigh when I went recently and as I have pre existing conditions phoned them up first. They told me that as long as I could answer the questions on the form properly and truthfully then I would be covered. If you mislead or lie to them then the cover would be void. If you have picked an insurance company give them a ring first to make sure. I answered all the questions on the phone then the bloke on the other end told me to use the form on-line as it would be cheaper because if he did it on the phone he would have to charge booking fee. In these cases it is always better to speak to them first to make sure you will be covered. It can get expensive otherwise.
Than you.I have filled in about 4 on-line forms for pre-existing problems,however, nothing is mentioned about disablement or Phantom Pain.But to be sure I will ring them tomorrow.