Flattening of the distal femoral condyle is a commonly cited feature of knee OA. However, it is unknown whether this is a result of bone wear, or subchondral bone remodelling. Studies show that subchondral bone turnover is increased and remodelling of new bone is pathologic. Such bone is denser with thicker trabeculae, but is also softer and osteopenic. Could remodelling of pathological subchondral bone be the aetiology of flattened condyles? Unlike the hip, not much is known about the morphological parameters of the knee’s articular surface in influencing OA risk outcome. If flattening is the result of the early OA disease process, mechanical stress to the joint will increase due to numerous causes, which will also be discussed.

The common sites of wear in knee OA include the distal femoral condyles, and the anteromedial portion of the medial tibia plateau. This study analysed the morphometry of these segments with the aim of quantifying any morphological changes in early OA.

The findings were that the extension facets in early OA are indeed flattened, even before the onset of bone to bone contact. Such flattening is hence part of the pathomorphological positive feedback loop, aggravating mechanical conditions early in the disease process.