Knee deformity in rheumatoid arthritis is closely correlated with generalized osteoporosis

To examine the relationship between knee deformity and osteoporosis in women with rheumatoid arthritis (RA), bone mineral density (BMD) in the lumbar spine and distal radius was measured using dual X-ray absorptiometry, and knee deformity (valgus or varus deformity) was measured using plain radiograms in 55 women with RA. Associations between knee deformity and BMD, disease related variables, including RA stage, RA duration, age, cumulative doses of administered glucocorticosteroids, body mass index, or postmenopausal period were evaluated. Cut-off values of the BMD defining RA patients with knee deformity were very close to the BMD value corresponding to 70% of young adult mean in the lumbar spine and distal radius. The femorotibial alignment was significantly correlated with age and deformity of the proximal tibia. Deformity of the proximal tibia was negatively correlated with the radial BMD and lumbar BMD. Deformity of the proximal tibia showed a significant difference between the groups of less than 5 years after menopause and the group of 5-10 years after menopause. We concluded that knee deformity in RA derived from deformity of the proximal tibia, and it was closely correlated with generalized osteoporosis.