Crab apple root nodules

Repotting a crab apple today and I discovered a whole load of nodules on the roots. Does anyone know what this is?

They look more like gall than nodules. Is the tree healthy, what does the overall look of the tree?
If they are nodules, they are beneficial, I have seen them on a few trees roots.
Here is some info, the article is about alder but it crosses over to all species