We observed the difference in microstructure between postmenopausal women with OA and OP, which might relate to the opposite bone defects in OA and OP. BV/TV might play an important role in mechanical properties of the subchondral bone in either OA or OP.

Objective. Osteoarthritis (OA) and osteoporosis (OP) of the hip rarely occur in the same patient. The purpose of this study was to determine whether this difference might be attributable to the different quantity and quality of subchondral cancellous bone in the two conditions.Methods. Subchondral cancellous bone from the femoral head was obtained at the time of hip arthroplasty from 60 postmenopausal women, 30 with OA and 30 with OP. In each group, 10 specimens were subjected to compressive fatigue loading and 20 were left nonloaded. Specimens were examined by compressive mechanical testing, micro-computed tomography scanning, fluorescence microscopy, and nanoindentation techniques.Results. Both the ultimate stress and the elastic modulus of cancellous bone from OA patients were significantly higher than those of cancellous bone from OP patients (P < 0.05). Compared to cancellous bone from OP patients, the bone volume fraction and trabecular thickness were significantly increased, but bone matrix mineralization was significantly decreased, in cancellous bone from OA patients (P < 0.05 for each comparison). The microcrack density was significantly higher in OP cancellous bone than in OA cancellous bone (P < 0.001), irrespective of fatigue loading. In addition, fatigue loading resulted in a significant increase in microcrack density in both OA and OP cancellous bone (P < 0.001). There was no significant difference in nanoindentation elastic modulus and hardness between cancellous bone from OA and OP patients, as well as between bones with and without fatigue loading.Conclusion. The difference in mechanical properties between OA and OP cancellous bone is attributed to different bone mass and bone structure. OP cancellous bone is susceptible to fatigue damage due to insufficient structure. However, increased bone volume and platelike structure provide OA cancellous bone a superior capacity to resist fatigue damage.Osteoarthritis (OA) and osteoporosis (OP) are two orthopedic disorders that usually result in high rates of morbidity and disability in people over the age of 50 years, particularly in postmenopausal women (1,2). Although OA and OP commonly occur in the elderly, they rarely coexist in a single patient (1,3). Healey et al (4) reported that only 4% of OP patients had significant osteoarthritis in the hip. It is well known that OP is associated with bone loss and microstructure deterioration, which can reduce bone strength and thereby increase the risk of fragility fracture (5). In contrast, the pathogenesis of OA remains a subject of controversy (6,7). In general, OA initially presents with destruction

Differential osteogenic potential and responsiveness to E2 of MSCs were found between postmenopausal women with OP and OA. These results may provide information for clinical application of MSCs in the differential setting of estrogen deficiency.