Can someone explain why old injuries act up?

I broke both my wrists a year and a half ago. One has a metal plate and screws. Both wrists were well healed and not causing me any issues until just the last week or so when my arm with the metal plate is painful and stiff. I assume this is TMS acting up, but why does it choose an old injury?

 

Lorimer Moseley (Pain neuroscientist) explains that it has to do with the brain remembering the injury and it will overprotect that body part.

 

Injuries are injuries: please get your wrist looked at and cleared by the Dr.

Then consider neural pathways. Your brain will click into places that get your attention, that have had lots of distracting communication with your nervous system. When you can simply let it go without attending to it (after having it medically cleared) it might go or, if your nervous system is still reacting to your internal state (you are still anxious, stressed: subconscious rage has been building up it might choose another spot to get your attention.
If everything with your wrist appears fine, you might need to do some TMS work to deal with your stress.

 

It has to be something you 'believe' in.