Osteoarthritis (OA) and osteoporosis (OP) are both common problems that affect life quality in aging society. It has been for decades of years to debate an inverse relationship between OA and OP. The objective of this paper was to compare structural properties of the articular calcified cartilage (ACC) and subchondral bone between postmenopausal women with OA and OP.

Eight femoral heads were taken from postmenopausal women during total hip replacement surgery due to primary OA. They were compared with nine femoral heads obtained from age-matched women with OP during hemi-hip arthroplasty surgery due to osteoporotic fracture of the proximal femur. Two-dimensional histomorphometric sections were prepared to measure the thickness of ACC and bone histomorphometric parameters. The ratio of ACC to the total articular cartilage (TAC) was also calculated in all bone specimens.

Osteoarthritic donors had higher ACC and the ratio of ACC to TAC (ACC: 117.69±28.16μm vs. 97.88±16.79μm, P=0.041; the ratio of ACC to TAC: 15.74% vs. 10.51%, P=0.023). Lower bone volume fraction (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N) and the ratio of nodes to termini (Nd/Tm) were demonstrated in donors with OP (BV/TV: 21.55±3.41% vs. 16.64±2.26%, P=0.003; Tb.Th: 121.33±16.11μm vs. 98.59±18.56μm, P=0.017; Tb.N: 2.41±0.73mm⁻¹ vs. 1.37±0.31mm⁻¹, P=0.001; Nd/Tm: 0.78±0.22 vs. 0.50±0.14, P=0.007). However, trabecular space (Tb.Sp) increased in these osteoporotic patients (Tb.Sp: 345.49±106.18μm vs. 652.09±159.71μm, P=0.0004).

The pathogenesis of OA and OP were influenced by differential properties of ACC and subchondral bone microstructure. Structural properties of the subchondral mineralized tissue supported that an inverse relationship existed between postmenopausal women with OA and OP.