The interrelationship between synovitis and bone damage in rheumatoid arthritis (RA) is a subject of controversy. Using magnetic resonance imaging (MRI), this study followed the bone changes in early RA and determined their relationship to synovitis.
Thirty-one patients with early RA who had swelling of the metacarpophalangeal (MCP) joints and 31 healthy control subjects with no clinical evidence of arthritis underwent MRI of the second through fifth MCP joints of the dominant hand by use of a 1.5T scanner. Coronal T1-weighted and T2-fat suppressed (FS) sequences were performed to evaluate bone edema, and gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) pulse sequences were obtained to evaluate synovitis. Bony abnormalities were described as bone edema (low signal on T1-weighted sequences and intermediate/high signal on T2 FS sequences adjacent to the bone cortex) or as bone cysts (circular juxtacortical abnormalities with low signal on T1-weighted images and with very high signal on T2 FS sequences). Contrast and noncontrast MRI films were scored in a blinded manner, and Fisher's exact probability test was used to determine differences between groups.
Twenty-one of the 31 RA patients (68%) had bone edema, which was seen in 43 of 124 joints (35% of joints) and 3 of the 31 control subjects had bone edema seen in 3 of 124 joints (2% of joints) (P < 0.0001). Thirty RA patients (97%) had Gd-DTPA-confirmed MCP joint synovitis, and bone edema was seen in 40 of the 75 joints with Gd-DTPA-proven synovitis (53%), but in only 3 of 49 without (6%) (P < 0.0001).
MCP joint bone edema is present in the majority of patients with RA at presentation, but is seen only occasionally in normal control subjects. The fact that bone edema occurred rarely in the absence of synovitis in patients with RA suggests that bony changes in RA are secondary to synovitis.