I'm a complete noob when it comes to Houdini. Every tutorial I watched on Houdini Muscle seems to have their own joints setup inside of Houdini. This way they can select individual joints and constrain the muscle handles to those because that joint chain shows up in the "obj" tab. I imported a custom FBX animation and I'm only allowed to select individual joints inside the geo node. The muscle nodes however are built outside in the "obj" tab. Is there any way I can select individual joints to constrain the muscle handles to?

This is only with the legacy muscle system right? The new one is all in SOPs and doesn't use OBJ at all.