[Osteoporosis and osteoarthritis--is there really an inverse relation?]

Increasing bone mineral density (BMD) has been found in several studies in patients with osteoarthritis (OA). Therefore, the simultaneous occurrence of osteoporosis (OP) and OA is denied by many clinicians. Because of our clinical impression, however, we suggest that we have to consider a common occurrence. In the present study we have examined the relationship between osteoathritis of the knee or the hip and osteoporosis.

The BMD of the lumbar spine and the proximal femur of 117 OA patients (82 postmenopausal female patients aged 50-83 and 35 male patients aged 36-86 years) who subsequently required hip or knee replacements, but were otherwise healthy, was measured by dual-energy X-ray absorptiometry (DXA; Hologic QDR-2000). The results are given as required by the WHO and the new German guidelines of the DVO. The BMD was measured and categorised in a sex-related manner and the occurrence of disuse osteoporosis on the affected limb was examined. Furthermore, a comparison was made in the level of BMD between the OA of the involved hip or knee.

There was a high occurrence of low BMD among the patients. 23.2 % of the women were affected by OP. This reflects the normal distribution of OP in the female population. 20 % of the male patients had occult OP. This is astonishingly high. Osteopenia was measured for 37.1 % of the male patients and 42.7 % of the female patients. Age proved to be a significant factor in the degree of BMD. Neither a disuse osteoporosis, nor a significance in the OA-affected joint to the degree of BMD, could be proven.

We cannot support the hypotheses that OA prevents OP. Moreover, the occurrence of OP in our study reflected the incidence of OP in the average female and was astonishingly high in the male population; this does not support the hypothesis that the two conditions are mutually exclusive. Also a lower risk of fractures among OA patients cannot be concluded. There is current open discussion whether a known BMD should influence the decision for a cemented or an uncemented prosthesis.