The phenotypic spectrum of COL2A1-related diseases is very broad and includes mainly spondyloepiphyseal dysplasia congenita (SEDC, OMIM#183900), Kniest dysplasia, spondyloperipheral dysplasia (SPPD, OMIM#271700), osteoarthritis with mild chondrodysplasia (OSCDP, OMIM# 604864), and spondyloepiphyseal dysplasia-Strudwick type (SED-ST, OMIM#184250). The gene discussed is COL2A1; the disease is osteoarthritis.