Cicuttini F et al. (2005) Comparison of conventional standing knee radiographs and magnetic resonance imaging in assessing progression of tibiofemoral joint osteoarthritis. Osteoarthritis Cartilage 13: 722–727

Investigators in Australia have suggested that cartilage volume, as measured by MRI, might be a better predictor of joint replacement in patients with osteoarthritis than radiographic joint-space width (JSW). The current 'gold standard' for assessing anatomic progression of osteoarthritis is JSW, but increasing interest in directly measuring cartilage volume prompted the comparison of these two methods.

In the longitudinal trial, 28 osteoarthritis patients had MRI and a weight-bearing radiograph at baseline and again after approximately 2 years. A potential limitation of the trial was the use of standing rather than semiflexed radiographs, although the method was optimized by including only patients who had satisfactory alignment in their radiographs at baseline and follow-up.

The data from the study showed that there was a modest but statistically significant correlation between radiographic minimum JSW and tibial and femoral cartilage volume at baseline, but there was no correlation between minimum JSW and cartilage volume in any of the cartilage plates over time. The authors comment that this lack of longitudinal correlation highlights the problem of using the one-dimensional measure, JSW, to indirectly measure three-dimensional structures. The data from the trial also revealed a trend for change in medial tibial cartilage volume, but not JSW, to be associated with joint replacement over 4 years. Further work using semiflexed radiographs in a larger sample size is required to verify the findings of this study.