A total of 979 women from the Chingford general population survey were studied to examine the hypothesis that osteoarthritis (OA) and osteoporosis are inversely related.
All women had radiographs of the hands and knees. A total of 579 also had AP radiographs of the lumbar spine which were graded for the presence of osteophytes. All women had bone densitometry performed at the lumbar spine (L1-L4) and femoral neck. Mean bone densities (BMD) were compared between those with disease and those with no disease at any other sites. All results were adjusted for age and body mass index (BMI).
All OA groups had significantly higher bone density than controls at the lumbar spine. For distal interphalangeal (DIP) OA (n = 140) the difference was +5.8% (+3.0, +8.6), for carpometacarpal (CMC) OA (n = 160) +3.0% (+0.1, +5.9), for knee OA (n = 118) +7.6% (+4.3, +10.9), and lumbar spine OA (LSOA) (n = 194) +7.8% (+6.0, +8.8). Those with generalised OA (GOA n = 22), a combination of knee, DIP and CMC OA had an increase of +9.3 (+2.0, +16.6). For the femoral neck BMD was also increased significantly ranging from +2.5% for the CMC, +6.2% for the knee and +6.3% in the lumbar spine OA group. The risk of knee OA for women in the top tertile of BMD was 2.13 (1.15-3.93). Additional adjustment for other confounders such as smoking, alcohol, exercise, HRT, social class and spine osteophytes did not alter the results.
These results suggest that small increases in BMD are present in middle aged women with early radiological OA of the hands, knees and lumbar spine. These data support the hypothesis that the two conditions are inversely related, although the mechanisms remain unclear.