Fibromyalgia and Costochondritis – a pain in the chest! Costochondritis is inflammation of the cartilage that connects the rib cage to the breastbone. The pain caused by costochondritis can be severe with stabbing pain that often mimics a heart attack. The ribs are connected to the breastbone by tough, protective tissue called cartilage. When this cartilage becomes inflamed, the condition known as Costochondritis or Costosternal Chondrodynia wreaks havoc. And for may Fibro s