How to monitor the local rotation of a bone in blueprint?

Is there any way I can “get” the local rotation of a bone in blueprint? I intend to use it to alter morph targets automatically depending on the current rotation of certain bones. For example, making a muscle flex as the arm is bent. I know how to make this happen manually in blueprint using a timeline curve and a play animation node, but I’d like to set up an automatic system so it works dynamically with an animation blueprint.

I did find a way to get the rotation for a bone of a posable mesh, but that isn’t what I need. I also found a way to monitor the world rotation of a socket attached to a bone, but that doesn’t help me either. Unless there is some way to compare the world rotation of the socket of the arm with the socket of the shoulder and make some sense of it, I don’t think it’ll work that way.

Just getting the location rotation of the bone would be best.

Stumbled across this and saw there was no answer.

I’m working in Unreal 4.17 and what is there is the “Get Socket Transform” node, and you can change the “Transform Space”.

The target needs to be the Skeletal Mesh Component.