Osteoarthritis protects against femoral neck fracture: the MEDOS study experience.

The relationship between osteoarthritis and osteoporosis (hip fracture) was studied using the data from the MEDOS study, a large prospective epidemiological study of femoral neck fracture patients and age-matched controls in the Mediterranean area. Osteoarthritis was found to be protective against hip fracture in both men and women, with a significant reduction of the relative risk factor for osteoporosis (relative risk = 0.48 and 0.68, respectively, p < 0.001). The age-adjusted relative risk factor for osteoporosis remains even after adjustment for body mass index, indicating that body mass index and osteoarthritis are independent relative risk factors for hip fracture. The mean age of the group with co-existent osteoarthritis and hip fracture was significantly higher for both men and women, compared to the group with osteoporosis alone. This indicates that if osteoarthritic subjects develop osteoporotic fracture, they do so at a later age. The osteoarthritic cases compared to controls and hip fracture cases were significantly smaller in stature in both sexes, and women had a significantly higher body weight and body mass index. Extra-capsular hip fracture was significantly more frequent in cases with concomitant osteoarthritis. These findings confirm earlier observations that osteoarthritis and osteoporosis are two distinct diseases and not phenomena related solely to aging.