Despite the significant limitations associated with the radiological assessment of OA (Table 1), X-rays have been routinely used as the gold standard to assess the progression of OA. In particular, a reduction in the JSW is regarded as the hallmark of disease progression. Whereas cross-sectional studies examining the association between BMI and radiological JSW have reported conflicting results (10,11), obesity has been consistently associated with a longitudinal reduction in the JSW.
A 12-yr follow-up study found that among people with knee OA, larger body mass indices were a risk for a reduction in the JSW, and therefore the radiological progression of OA (OR: 11.1; 95% CI: 3.3-37.3) (51).
Although obesity is a risk factor for longitudinal radiological JSN, the assessment of the JSW as an outcome measure for the progression of OA is often insensitive. Raynauld et al. found that over a 2-yr period, radiological assessment was unable to distinguish significant changes in the JSW in people with knee OA, despite a significant loss of articular cartilage volume (52). In contrast, MRI studies have revealed that as little as 2% change in cartilage volume may be reliably detected when a maximum of 6 individuals (patella), 10 (femur), 28 (medial tibia), and 33 (lateral tibia) are followed longitudinally (53). Although obesity is a risk factor for the progression of radiological JSN, it would appear that the assessment of cartilage volume measured from MRI is a more sensitive indicator of disease progression in OA. Nevertheless, no studies have directly assessed the relationship between obesity and longitudinal loss of articular cartilage volume from MRI assessment. Moreover, no longitudinal study has examined the specific parameters of body composition, such as fat distribution, and the risk of the progression of knee OA. Further work is required in these areas.
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