The aim of this study was to examine the possible association between different grades of joint effusion (JE) and osteoarthritis (OA) in temporomandibular joint (TMJ) anterior disk displacement without reduction (ADDwoR).A sample of 101 female patients 20-40 years of age with unilateral TMJ ADDwoR were retrospectively reviewed. JE and OA were diagnosed with magnetic resonance imaging (MRI). JE was subdivided into three different grades: grade 0, no or minimal effusion; grade 1, moderate effusion; and grade 2, extensive effusion. Eight categories of degenerative changes were used for screening for the existence of OA. Cases with no less than one type of degenerative change were diagnosed as OA.In all, 71 patients (70.3%) were diagnosed as having OA in the joints with disk displacement. In the univariate analysis, the proportion of subjects with non-JE (grade 0) was higher in the OA group (p = 0.003), while the proportion of subjects with extensive effusion (grade 2) was lower in the OA group (p = 0.02). In the multivariate logistic regression analysis, non-JE was independently associated with the development of OA (odds ratio = 5.68, 95% confidence interval = 1.10-29.37, P = 0.04).The results suggested that non-JE was associated with OA in the joints with ADDwoR.