Current evidence demonstrates focal synovial inflammation occurs during development of post-traumatic osteoarthritis (PTOA), suggesting synovium either reacts or contributes to adjacent articular damage. However, baseline measures for distinguishing early synovial inflammation from normal synovium have yet to be established. The hypothesis was that synovial samples from both hind limbs of immature (n=5) and skeletally mature sheep (n=5) would have no histological or molecular evidence of inflammation. Histological grading of synovium from four anatomic locations confirmed its homogeneity and absence of synovitis as scores were well below quantitative thresholds of "mildly inflamed". Interestingly, molecular quantification of six biomarkers of inflammation in normal synovium were low but not zero and varied 1 – 3 fold between different locations. The findings suggest a minimum 3 – fold difference in such biomarkers is required to establish synovitis. Baselines of normal sheep synovial histology and molecular biomarker expression for future studies of PTOA onset have been established.