Radiographic joint space width in individuals with hand osteoarthritis: Are their "healthy" joints really healthy?

We aimed to investigate the systemic nature of hand osteoarthritis (OA). We hypothesized that people who suffer from hand OA would display narrower radiographic joint space width (JSW) - not only in joints with apparent radiographic OA but also in their unaffected "healthy" joints.

We examined 3394 participants from the Osteoarthritis Initiative with available dominant hand radiographs at baseline. Cases were defined as having interphalangeal OA (IPOA) based on a Kellgren and Lawrence (KL) score of ≥2 in two or more finger joints, whereas controls did not have IPOA. We used custom software to make JSW measurements of the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints in fingers 2-5 per hand. In joint-level analyses, we included only KL score=0, allowing us to compare all joints without IPOA in cases and controls. We used generalized estimating equation models to compare JSW between both groups, adjusted for age, gender, metacarpal length, and joint type.

Finger joints without radiographic OA had significantly narrower JSW in the IPOA group compared to finger joints in the control group (p < 0.001). The differences were significant across all joint types and for both total JSW measurements as well as for central and lateral sub-regions within each joint group (p < 0.001).

Unaffected finger joints in people with IPOA had narrower joint space than joints of healthy controls. This implies a systemic nature of hand OA, in which people may have a predisposition for general cartilage deterioration.