A number of previous studies have reported an inverse relationship between osteoarthritis and osteoporosis. However, the association has remained controversial because osteoarthritis in hand joints seems to associate differently from osteoarthritis in weight-bearing joints with bone mineral mass. We studied osteoarthritis in distal interphalangeal (DIP) joints and osteoarthritis in the base of the thumb (CMC-1) for their cross-sectional associations with metacarpal cortical bone mineral mass, and for their prediction of calcaneal broadband ultrasound attenuation.
A population sample of 8000 Finns aged 30 yr and over was invited to a comprehensive health examination in 1978-1980; 90% complied. Hand radiographs were taken from 3568 participants to diagnose osteoarthritis in various hand joints, and to determine two indicators of cortical bone mineral mass, the combined cortical thickness (CCT) and the metacarpal index (MCI). Calcaneal broadband ultrasound attenuation was measured 20 yr later in 340 of these participants with the Sahara sonometer.
In the cross-sectional setting, osteoarthritis in the DIP joints and osteoarthritis in the base of the thumb (CMC-1) were significantly associated with low CCT and low MCI. These associations were proportional to the radiological severity of osteoarthritis. In the follow-up setting, symmetrical DIP osteoarthritis adjusted for age, sex, body mass index, smoking, education, workload and MCI significantly predicted low values of broadband ultrasound attenuation.
Our results indicate a direct relation of both radiological DIP osteoarthritis and CMC-1 osteoarthritis with low cortical bone mineral mass, in proportion to the severity of osteoarthritis. The presence of symmetrical DIP osteoarthritis, a possible indicator of generalized osteoarthritis, suggests an increased risk of osteoporosis over time.