Patients grouped according to progression of magnetic resonance imaging (MRI) to xray erosions after one year
| Group 1 | No erosions on MRI |
| Group 2 | Erosions on MRI (at baseline or 1 year) but no progression at those sites to x ray erosions seen 1 year later |
| Group 3 | Erosions on MRI at baseline and/or 1 year. 30% or less progress at those sites tox ray erosions seen 1 year later |
| Group 4 | Erosions on MRI at baseline and/or 1 year. >30% progressat those sites to xray erosions seen 1 year later |