Importance of the changes in joint effusion shown by magnetic resonance imaging before and after arthroscopic lysis and lavage of the temporomandibular joint.

We investigated the changes in the amount of joint effusion estimated from T2-weighted magnetic resonance imaging (MRI) before and after arthroscopic lysis and lavage of the temporomandibular joint (TMJ). We studied 29 consecutive patients, each with internal derangement and osteoarthritis in one TMJ. Before operation, the MRI showed joint effusions in 22 of the patients (76%). After operation, the amount of the effusion decreased in 16 and increased in 2 patients. Effusions developed postoperatively in four of the seven patients who had no effusion before operation. In four of the six patients in whom the effusion increased, the symptoms had almost resolved by the time the MRI was taken. There was no significant correlation between changes in the amount of joint effusion and the clinical condition of the patients before and after the operation. In conclusion, changes in the amount of joint effusion in the TMJ are not related to the patient's clinical condition.