Each bone (wrists: distal radius, distal ulna, carpal bones, metacarpal bases; MCP joints: metacarpal heads, phalangeal bases) is scored separately

The scale is 0–10, based on the proportion of eroded bone compared to the “assessed bone volume,” judged on all available images: 0 = no erosion; 1 = 1–10% of bone eroded; 2 = 11–20%, etc. For long bones, the “assessed bone volume” is from the articular surface (or its best estimated position if absent) to a depth of 1 cm, while in carpal bones it is the whole bone

In case a bone is fused with another bone, bone erosion is scored as 10 in the bone

Each bone is scored separately (as for erosions)

The scale is 0–3 based on the proportion of bone with osteitis, as follows: 0 = no osteitis; 1 = 1–33% of bone with osteitis; 2 = 34–66%; 3 = 67–100%

Synovitis is assessed in 3 wrist regions (1. the distal radioulnar joint; 2. the radiocarpal joint; 3. the intercarpal and carpometacarpal joints) and in each MCP joint. The first carpometacarpal joint is not scored

The scale is 0–3. Score 0 is normal, while 1–3 (mild, moderate, severe) are by thirds of the presumed maximum volume of enhancing tissue in the synovial compartment

Joint space narrowing is assessed at 17 locations in the wrist, between distal radius and carpal bones (2 sites), between the carpal bones (except the pisiform; 10 sites), and between carpal bones and each metacarpal bone (5 sites), and in each MCP joint

The scale is 0–4, as follows: 0 = no narrowing; 1 = focal or mild (< 33%) narrowing; 2 = moderate (34–66%) narrowing; 3 = moderate to severe (67–99%) narrowing; 4 = ankylosis

In the wrist, tenosynovitis is assessed at 6 extensor tendon compartments and 3 flexor tendon compartments, between the radioulnar joint and the hook of hamate. At the level of the MCP joints, flexor tendons are assessed in an area from 1 cm proximal to 1 cm distal to each joint

Tenosynovitis is scored based on the maximum width of the effusion and/or tenosynovial enhancement measured perpendicularly to the tendon

The scale is 0–3, as follows: 0 = no; 1 = < 1.5 mm; 2 = ≥ 1.5 mm but < 3 mm; 3 = ≥ 3 mm peritendinous effusion and/or postcontrast tenosynovial enhancement