Knobbly apple tree

Anybody know what might be causing these knobbly bits on this apple tree? It's auite extensive, on much of the main branches. Google searching cones up with either crown gall or burrs, although i'm not sure. I don't know much of the tree's history. Was in the garden in a pretty poor state when we bought the house. Trying to bring it back to a healthy state, but wondering whether it just needs to come down. Thanks!

Last edited: 24 February 2018 21:23:26