Patellofemoral osteoarthritis: New insights into a neglected disease

Knee osteoarthritis (OA) is characterized by joint changes, such as cartilage degradation, subchondral sclerosis and osteophyte formation around the margin of the articular surface. The knee joint has three compartments: the medial tiblofemoral, the lateral tibiofemoral and the patellofemoral. Although most epidemiological studies have predominantly examined risk factors for tibiofemoral rather than patellofemoral disease, pain associated with knee OA commonly emanates from the patellofemoral joint. Evaluating the patellofemoral joint using radiography is problematic, which may have led to the paucity of data on patellofemoral OA. However, the advent of magnetic resonance imaging has enabled direct visualization of the entire knee joint and has given new insights into the pathogenesis of joint pathologies, such as OA. This discussion aims to compare and contrast patellofemoral and tibiofemoral OA and, thus, highlight that they are independent entitles and, as such, must be examined as separate pathological processes. Moreover, this discussion demonstrates how new imaging modalities are providing insight into the pathogenesis of patellofemoral OA.