Purpose: The purpose of this study was to find the relationship among the joint status, pain and effusion in patients with temporomandibular joint disorders. Materials and Methods: Materials included 406 patients (812 joints) with clinical records and bilateral TMJ MRIs in TMJ clinic, Yongdong Severance Hospital. All joints were classified in 4 groups in MR images according to the disc status of joint; normal disc position, disc displacement with reduction (DDcR), early and late stage of disc displacement without reduction (DDsR), and also 2 groups according to the bony status of joint; normal bony structure and osteoarthrosis. MR evidence of joint effusion was categorized in 4 groups according to its amount. To determine the relationship between joint pain and joint effusion, 289 patients with unilateral TMJ symptoms were selected from total materials. Result: Joint effusion was found 8.0% in normal disc position, 32.6% in DDcR, and 59.2% in DDsR (83.1 % in early state and 23.1 % in late stage). Joint effusion was found 39.7% in osteoarthrosis and 35.0% in normal bony structure. Joint effusion was more found in the painful joints (49.8%) than in the painless joints (22.4% )(p<0.001). Joint effusion in the early stage of DDsR only was more found significantly in painful joints (91.9%) than in painless joints (62.1 %) (p<0.001). Conclusion : MR evidence of joint effusion might be related to disc displacement regardless of the presence of osteoarthrosis, and the early stage of DDsR was found more frequently combined with joint effusion and joint pain.