Structural investigation in subchondral bone of osteoarthritic knee: Phosphorous K-edge XAS

The present study reports a structural change of subchondral bone samples obtained from the patients who suffer from osteoarthritic knee (OA). The structural study was undertaken by comparison between controlled patients aged below 50 years old and OA patients aged over 50 years old. By employing Synchrotron-based X-ray fluorescence (SR-XRF) and X-ray absorption spectroscopy (XAS) techniques including X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), the evidence of bone changes in term of Calcium–Phosphorus (Ca–P) contents were revealed. SR-XRF results excited at 2350 eV for P elements were used to clearly identify the amount of phosphorus contents in subchondral bone structure. The result showed the P contents in patients aged above 50 years old (OA) are lower than controlled patients. The depth information obtaining from both XANES and EXAFS results at P K-edge is related to electron transitions and structural modification especially around P ions at different ages. Lower Ca–P proportions which are caused the osteoporosis were obviously found in the elder patients. In addition, the majority amorphous structure of Ca–P is mainly found in all bone samples.