Preclinical and Early Osteoarthritis

The term early osteoarthritis (OA) is often used to refer to mild or moderately severe radiographic OA. More recently, the term early OA has been used to refer to preradiographic or even earlier phases of disease. Diagnosis of OA in its early preradiographic stages could improve the likelihood of disease modification and thereby reduce medical costs, morbidity, and disability. The advent of sensitive imaging techniques has provided concrete evidence for joint structural abnormalities predating the quintessential radiographic changes we associate with OA. However, conventional OA risk factors function poorly for detection of preclinical and early OA. Therefore, it is currently difficult to define asymptomatic early stage (preclinical) OA in the absence of imaging abnormalities. Because not all radiographic OA progresses to a severe grade of disease or results in joint replacement, by inference, likely not all preclinical or preradiographic OA is expected to progress to early OA and more advanced stages of disease. The trajectory from preclinical to preradiographic to radiographic OA is influenced by the robustness of the endogenous cartilage repair responses, that vary by joint site, and genetic polymorphisms of growth factors implicated in OA susceptibility. The paradigm of joint tissue and biomarker alterations after joint injury is expected to provide a scenario for developing diagnostic algorithms for the early detection of idiopathic OA.