Hand joints without radiographic osteoarthritis maintain their joint space width over 4 years despite what's happening elsewhere in the hand

<bold>Objectives: </bold>We aimed to determine if hand osteoarthritis is characterized by systemic cartilage loss by assessing if radiographically normal joints had greater joint space width (JSW) loss during four years in hands with incident or prevalent osteoarthritis elsewhere in the hand compared with hands without osteoarthritis. <bold>Methods: </bold>We used semi-automated software to measure JSW in the distal and proximal interphalangeal joints of 3,368 participants in the Osteoarthritis Initiative who had baseline and 48-month hand radiographs. A reader scored 16 hand joints (including the thumb-base) for Kellgren-Lawrence (KL) Grade. A joint had osteoarthritis if scored as KL >= 2. We identified three groups based on longitudinal hand osteoarthritis status: 1) no hand osteoarthritis (KL < 2 in all 16 joints) at the baseline and 48-month visits, 2) incident hand osteoarthritis (KL < 2in all 16 joints at baseline and then >= 1 joint with KL >= 2 at 48-months), and 3) prevalent hand osteoarthritis (>= 1 joint with KL >= 2 at baseline and 48-months). We then assessed if JSW in radiographically normal joints (KL = 0) differed across these three groups. We calculated unpooled effect sizes to help interpret the differences between groups. <bold>Results: </bold>We observed small differences in JSW loss that are unlikely to be clinically important between radiographically normal joints between those without hand osteoarthritis (n = 1054) and those with incident (n = 102) or prevalent hand osteoarthritis (n = 2212) (effect size range: -0.01 to 0.24). These findings were robust when examining JSW loss dichotomized based on meaningful change and in other secondary analyses. <bold>Conclusions: </bold>Hand osteoarthritis is not a systemic disease of cartilage.