Background: Primary synovial chondromatosis (PSC) is a rare idiopathic pathology characterized by the formation of osseocartilaginous nodules within synovial joints, tendons, or bursae. The mineralization pattern of PSC nodules is poorly understood and has yet to be investigated using elemental analysis. Mapping this pattern could elucidate the progression of the disease.Materials and methods: PSC nodules discovered during dissection of a formalin fixed donor were analyzed. Scanning electron microscopy paired with energy dispersive X-ray spectroscopy (SEM-EDS) was used to quantify calcium and phosphorus levels to distinguish mineralized components from cartilage, indicated by increased carbon and oxygen concentrations.Results: Nine nodules with average dimensions 1.76cm x 1.25cm were identified in the semimembranosus bursa. SEM-EDS demonstrated increased calcium phosphate levels in nodular cores, while outer margins contained primarily carbon and oxygen. Quantification of these elements revealed nodular peripheries to contain 68.0% carbon, 30.2% oxygen, 0.8% calcium, and 1.0% phosphate, while cores were comprised of 38.1% carbon, 42.1% oxygen, 14.1% calcium, and 5.7% phosphate. Conclusions:Nodules were found to have mineralized cores embedded within a cartilaginous matrix. This pattern suggests disease progression is facilitated by endochondral ossification, opening the potential for new therapeutic techniques.