The objective of this study was to compare single-needle arthrocentesis with the conventional two-needle arthrocentesis, as well as the additional intracapsular injection of hyaluronic acid or platelet-rich fibrin. A total of 96 patients with established osteoarthritis (OA) (n = 48) or with internal de-arrangement (DD) (n = 48) were assigned single-needle arthrocentesis with distension of the joint or conventional two-needle arthrocentesis with or without intracapsular injection of the medication (hyaluronic acid (HA) or platelet-rich plasma (PRP)) performed every month over a period of 6 months. The maximum mouth opening and pain, as measured by the visual analog scale (VAS), were compared. Each group exhibited significant improvement, i.e., a decrease in pain and an increase in mouth opening. The single-puncture technique provided similar pain reduction as the two-needle approach but provided significantly better results in terms of maximum mouth opening. The reduction in pain was similar when comparing the OA and DD cohorts; however, patients with disc displacement achieved significantly better mouth opening than OA. Intracapsular application of medication contributed to a significant decrease in pain in both HA and PRP groups, with platelet-rich fibrin being significantly superior to HA in terms of mouth opening improvement.