Studies in the homozygous osteogenesis imperfecta murine (oim/oim) model, which contains a nucleotide deletion in the Col1a2 gene resulting in nonfunctional proα2(I) collagen chains and the production of homotrimeric type I collagen [α(I)3] rather than normal heterotrimeric type I collagen [α1(I)2α2(I)], were the first to demonstrate an inherent muscle pathology as part of the pathophysiology of OI [3,31,32]. The gene discussed is COL1A2; the disease is osteogenesis imperfecta.