Our previous work has shown that near-infrared diffuse optical tomography has the potential to be a clinical tool in diagnosis of osteoarthritis. Here we report a study of 38 joints from 38 females, including 20 OA and 18 healthy joints. The quantitative results obtained show that there exists clear difference between OA and healthy joints in terms of the ratio of optical properties of the joint soft tissues to that of the associated bone. Statistic analysis of these clinical data is also presented. © 2009 SPIE.