Appendicular bone mass and knee and hand osteoarthritis in Japanese women: a cross-sectional study

BACKGROUND It has been reported that there is an inverse association between osteoarthritis (OA) and osteoporosis. However, the relationship of bone mass to OA in a Japanese population whose rates of OA are different from Caucasians remains uncertain. METHODS We studied the association of appendicular bone mineral density (second metacarpal; mBMD) and quantitative bone ultrasound (calcaneus; stiffness index) with knee and hand OA among 567 Japanese community-dwelling women. Knee and hand radiographs were scored for OA using Kellgren-Lawrence (K/L) scales. In addition, we evaluated the presence of osteophytes and of joint space narrowing. The hand joints were examined at the distal and proximal interphalangeal (DIP, PIP) and first metacarpophalangeal/carpometacarpal (MCP/CMC) joints. RESULTS After adjusting for age and body mass index (BMI), stiffness index was significantly higher in women with K/L scale, grade 3 at CMC/MCP joint compared with those with no OA. Adjusted means of stiffness index and mBMD were significantly higher in women with definite osteophytes at the CMC/MCP joint compared to those without osteophytes, whereas there were no significant differences for knee, DIP and PIP joints. Stiffness index, but not mBMD, was higher in women with definite joint space narrowing at the CMC/MCP joint compared with those with no joint space narrowing. CONCLUSIONS Appendicular bone mass was increased with OA at the CMC/MCP joint, especially among women with osteophytes. Our findings suggest that the association of peripheral bone mass with OA for knee, DIP or PIP may be less clearcut in Japanese women than in other populations.