Bone mineral density and bone turnover in patients with knee osteoarthritis compared with generalized osteoarthritis

The aim of this study was to investigate bone mineral density (BMD) and bone turnover in patients with primary knee osteoarthritis (KOA) and to compare them with generalized OA (GOA) and nonGOA patients. A total of 88 postmenopausal primary KOA patients were studied. OA was graded by using knee radiographs. BMD of the lumber spine, femur, and radius, and biochemical markers of bone turnover, pyridinoline (Pyr), deoxypyridinoline (Dpyr), CTx, and osteocalcin were compared among each grade. BMD was also compared with 88 normal controls who were age and weight-matched. In 88 KOA patients, 56 were divided into 28 GOA and 28 non-GOA groups by grading hand radiographs. BMD and biochemical markers were compared between GOA and non-GOA. KOA patients had higher BMD at several skeletal sites compared with age- and weight-matched normals. A significant difference of BMD between each grade was observed between grades 0-1 and 3 (0.774 +/- 0.143 versus 0.940 +/- 0.185 g/cm(2), P < 0.001), grades 2 and 3 (0.781 +/- 0.125 Versus 0.940 +/- 0.185 g/cm(2), P < 0.01) in the spine, and between grades 0-1 and 3 (0.505 +/- 0.100 versus 0.563 +/- 0.127 g/cm(2), P < 0.05) in the trochanter. A significant difference of biochemical bone markers was observed between grades 0-1 and 3 (P < 0.05) and between grades 2 and 3 (P < 0.05) in Pyr and grades 0-1 and 3 (P < 0.05) and between grades 1 and 4 (P < 0.05) in Dpyr, but not in osteocalcin and CTx. GOA patients had higher BMD of the spine (0.902 +/- 0.175 versus 0.747 +/- 0.138 g/cm(2), P < 0.01), trochanter (0.535 +/- 0.107 versus 0.480 +/- 0.107 g/cm(2), P < 0.05), and one-third of the radius (0.526 +/- 0.068 versus 0.472 +/- 0.089 g/cm(2), P < 0.05) and had significantly higher biochemical markers in Pyr and Dpyr than non-GOA patients. It is concluded that KOA patients had higher BMD at several skeletal sites. Biochemical bone markers were influenced by some degree of cartilage damage in OA patients. This tendency was stronger in GOA patients than in non-GOA patients.