I write this as I enter week 3 of fractured tibia recovery. I am feeling slightly better. Good things are happening in my body. I'm moving from the inflammatory to the reparative stage of bone healing. This is when the blood clots that form at the site of the fracture are replaced by something called a callus. A callus is a mass of mesenchymal stem cells that will differentiate into cells called chondroblasts and osteoblasts, the primary players in the formation of cartilage