“…However, for the prediction of KOA progression, although knees with moderate KOA at baseline were intentionally targeted, there was no specific inclusion criterion that was mostly employed. As reported in Table 3 , the criterion for knee inclusion was knees with KL = 1, 2 or 3 in three studies [ 27 , 29 ], with KL = 2 or 3 in five studies [ 28 , 41 , 42 , 43 , 45 ], or with KL ≥ 1 in three studies [ 44 , 46 ], and with KL ≥ 2 in two studies [ 33 , 35 ]. In order to have fair and valid comparisons of the performance of the proposed KOA prediction models, the KOA community should identify a unique definition of both KOA incidence and progression as well as standardize a specific inclusion criterion.…”