It's spasm of the intercostal muscles located between the ribs. It's not unique to ms alone. I've been told costochondritis (inflammation in the ribs) can bring it on. Pretty bad my gp wasn't the one to tell me that, but I lucked out and didn't get the hug.

Like you're wearing a corset that some sadist has pulled to untolerable level of tightness.

I get it a lot in the intercostal muscles between my ribs-left side mostly- my It is painful.

It feels like pressure or tightness around your rib cage. Can also be a little painful.. I wear rib belt as counter pressure. It helps a little.

GinaBeth thank you for that answer