I'm sorry but this is normal, ESA is not a walking test, it is a Mobility test! In addition to your walking it considers your ability to self-propel a manual wheelchair over the same distances, you do not need to be using a wheelchair or even to own one for it to be considered. SO even if you can show your walking is restricted, unless you can also show that you cannot self-propel the wheelchair you will still not score points.
Also, those assessing you will also consider any prosthesis that you normally wear.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems
