Osteoarthritis (OA) is perhaps the most common disabling joint affection in developed countries, and consequently a large burden to their health systems.¹ Furthermore, it is a growing global problem due to increasing life expectancy as well as obesity and smoking, all identified as risk factors for developing knee OA and knee pain.^2,3 Efforts to identify early stages of knee OA are gaining importance because of its prevalence and morbidity and the possible emergence of preventive or modifying interventions. However, radiographic delineation of OA at its onset is not a trivial problem as highlighted by the careful study of Mazzuca et al in this issue of the journal.⁴ In essence the paper shows that radiographically normal is not identical to anatomically normal. Thus the designation of the unilateral nature of knee OA in the Chingford study is not strictly correct.¹⁵ Nevertheless, the Chingford approach to studying early phases of progression and searching for methods to retard or stop this progression is useful and should be pursued.

“The Chingford approach to studying knee OA is not strictly correct but, nevertheless useful”

Recent work has provided new insight into the formation of cartilage and bone during embryonic development. This highly regulated process has bearing on the pathogenesis of OA. Collagen IIA, a splice variant of mature collagen type II, is formed in chondrogenesis.⁵ It is absent in adult healthy cartilage but can again be found in OA.⁶ This observation opens ways to search for biochemical signs of early OA which may be of clinical or scientific use. The problem that …