Certain fibril-associated collagens with interrupted triple helices (FACITs) associate with the surface of collagen fibrils, where they may serve to limit fibril fusion and thereby regulate fibril diameter (Ansorge et al. 2009, Gordon & Hahn 2010). Type XII and XIV colalgens are found in association with type I (Walchli et al. 1994) and type II (Watt et al. 1992, Eyre 2002).