Editorial: Valgus alignment and lateral compartment knee osteoarthritis: A biomechanical paradox or new insight into knee osteoarthritis?

The paper by Felson and colleagues (1) in this issue reports that valgus malalignment increases the risk of knee osteoarthritis (OA) x-ray progression, and incidence of lateral cartilage damage. Furthermore the paper suggests that even a relatively slight valgus alignment may cause lateral compartment osteoarthritis (OA), in part, by increasing the risk of meniscal damage. Given that the major percentage of the ambulatory load during walking is transferred to the medial compartment of the knee even for knees with slight valgus alignment, this study raises some important questions regarding the role of static frontal plane alignment and more specifically of ambulatory forces in the natural course of knee OA. Does this study present a possible biomechanical paradox or do these results point to the need for a deeper understanding of the role of ambulatory load in the pathomechanics of knee OA? This editorial will address this potential paradox by examining the role of mechanical factors in OA across scales ranging from full body ambulation to cell biology.