This study was performed to determine whether arthrocentesis therapy has different outcomes in three groups of patients with different temporomandibular disorders (TMDs). A clinical trial was conducted including 45 patients with 45 unilaterally affected joints divided into three groups (n=15): osteoarthritis (OA), disc displacement with reduction (DDWR), and disc displacement without reduction (DDWoR). All patients underwent the same arthrocentesis treatment protocol. The outcome variables, including visual analogue scale evaluations and measurements of mandibular motion (in millimetres), were recorded at baseline and at 1 and 6 months postoperative. Inter-group assessments showed significant short-term differences in joint sounds (P=0.016) and significant long-term differences in masticatory efficiency (P=0.046) and protrusive movement (P=0.048). The estimation of mean changes between baseline and long-term follow-up revealed significant differences in joint sounds (P<0.001), disruption in daily activities (P=0.002), maximum mouth opening (P=0.008), and protrusive movement (P=0.002) between the groups. Arthrocentesis therapy may be useful to improve clinical symptoms and range of mandibular movement in patients with all three types of TMD. However, the benefit of arthrocentesis may be greater for patients with DDWoR than for those in the other groups.