The aim is to compare the effectiveness of corticosteroid administration (dexamethasone) with a placebo (saline), following arthrocentesis of for the temporomandibular joint (TMJ). Twenty-eight participants with TMJ arthralgia, mainly related to osteoarthritis ae randomly assigned to two arms of a parallel double blind RCT. In both arms an arthrocentesis procedure is carried out, while a single dose intraarticular dexamethasone was delivered to participants in one arm. Saline was delivered in the other arm to serve as a control. Follow up visits were scheduled after 1, 3 and 24 weeks. During each visit TMJ pain (on a 100mm VAS) and joint stiffness (mouth opening in mm) are scored. Generalized estimating equations (GEE) are used for statistical analysis.

The arthrocentesis procedure was performed under local anaesthesia and took place in a closed operation room under controlled conditions. After marking the points for insertion of the needles, a first 18 gauge injection needle was inserted into the upper intra-articular space of the TMJ. Correct positioning of the needle was determined by injecting and aspirating saline. Subsequently, a second 18 gauge needle was inserted into the upper joint space about 8-10 mm anterior of the first needle. Correct positioning of the second needle was confirmed by allowing injected saline to leave the joint through the first needle. After positioning of the needles, one needle was connected to a medical infusion system to passively allow isotonic saline of 37 degrees Celsius to enter the upper joint compartment. The other needle was connected to an outflow tube to allow the fluid to exit the joint. In about 15 minutes, approximately 300 ml saline passively flushed the joint. Thereafter, the inflow was stopped and the prepared syringe (see randomisation procedure) that contained either dexamethasone or saline was connected to the inflow needle. In this way, either 1 cc of dexamethasone or an equal amount of saline was washed through the joint in a blinded way. At the end of the procedure, the needles were removed from the joint, and after hemostasis by compression (if necessary) the skin overlying the TMJ was covered with a sterile band aid.

All patients were then instructed to avoid TMJ loading by following a soft diet for at least two weeks, then gradually advancing to more tough food. In addition, ibuprofen 600 mg 3dd was prescribed for the first 2-5 days to reduce any postoperative pain. All procedures were performed by one surgeon.

Follow up visits were scheduled after 1 (T1), 3 (T2) and 24 (T3) weeks.

Inclusion Criteria:

Pain localized in one of the TMJs (TMJ arthralgia).

Exclusion Criteria:

• No significant relief of pain within 10 minutes after anaesthesia (injecting 0,1 ml articaine 40 mg/ml) of the TMJ
• Past history of open surgery in the affected joint
• Known polyarthritis (mostly rheumatoid arthritis)
• Age under 18 yrs
• Ankylosis of the TMJ
• Reported pregnancy