The present invention is directed to a method for repairing defects in articular cartilage and, more particularly, to a new method for performing automated microfracture on subchondral bone to repair articular cartilage. The microfractured holes on the surface of the subchondral bone plate are formed with an automated process using a pneumatically driven orthopedic microfracture instrument. The instrument moves a fracture pin through the end of a guide tube until a sharp end of the fracture pin punctures or penetrates the subchondral bone plate and creates a microfracture or hole in the bone.