| Patient no. | Bone specimen | MRI bone oedema score | Histopathology report | |
| Reader 1 | Reader 2 | |||
| 6 | Left 1st metatarsal head, medial eminence | 6 | 6 | Moderately intense patchy lymphoplasmacytic infiltration in the subchondral marrow, patchy pannus formation over the articular cartilage and subchondral cyst |
| 7 | Right 5th metatarsal head | 2 | 2 | Thinning and focal necrosis of articular cartilage with marginal pannus formation with patchy aggregations of mature small lymphocytes in the subchondral region, plus subchondral cyst |
| 10 | Left 2nd metacarpal head | 0 | 0 | Degeneration and focal loss of cartilage and thin fibrovascular pannus formation, focal remodelling of subchondral bone with light mononuclear cell infiltration and slight marrow fibrosis |
| Left 3rd metacarpal head | 0 | 0 | Patchy loss of articular cartilage with thin fibrous pannus formation, irregular interface between articular cartilage and subchondral bone with prominent congested capillaries but no evidence of osteitis | |
| Left 4th metacarpal head | 0 | 0 | Degeneration of articular cartilage with thin fibrous pannus formation at joint margin, slight osteitis | |
| Left 5th metacarpal head | 0 | 0 | Degeneration of articular cartilage, thin fibrous pannus formation with slight focal osteitis and some remodelling of subchondral bone | |
| 11 | Left 1st metatarsal head | 1 | 2 | Focal disruption of the articular cartilage and a flask-shaped defect extending into the medullary space; the lining is composed of fibrous granulation tissue with telangiectatic new blood vessels and slight lymphocyte infiltration; elsewhere the normal articular cartilage is replaced by fibrous pannus and fibrocartilage |
*MRI bone oedema scored separately by 2 radiologists according to the extent and intensity of bone oedema at the site where bone was resected as follows: spatial extent of bone oedema; Grade 0 for none, Grade 1 for ⩽33%, Grade 2 for 34–66%, Grade 3 for 67–100% of area of bony site assessed. Intensity of bone oedema; Grade 0 = none, Grade 1 = moderate intensity, Grade 2 = high intensity. Total score comprises spatial extent×intensity scores. Maximum possible score per site = 6.