I'm assuming your risk list is in a document library. If yes, then if
someone checks out that document, others can view and take a copy of the
document but they cannot over-write the the SP copy with their copy.
Otherwise, there is no point to check-out.
If you are doing your risk list as a List (how I would do it), then to
do offline changes requries something which can synchronise offline
changes. AFAIK, SharePoint does not do that out of the box, but I use
Colligo (a 3rd party tool) to allow me to work offline while travelling
to update project Risk Lists.