Susceptibility to osteoarthritis (OA) is influenced by genetic mutations, many of which occur in genes associated with the development of synovial joints. In this Review, Linda Sandell proposes a theory that these mutations can be placed on a continuum—from obvious alterations that result in mild chondrodysplasia associated with early-onset OA to subtle changes that predispose to 'primary OA' later in life. This view is explained in the context of our current etiological understanding of OA, and how this knowledge could improve screening and treatment of patients is discussed.
