Introduction:
Temporomandibular joint might be affected by a divergent scope of disorders. The objective of TMJ imaging is to document any clinically suspected disorder of the joint and surrounding structures. MRI has become the gold standard TMJ Imaging. TMJ arthroscopy allow direct visualization of the joint with diagnostic capabilities during surgery

Aim of study:
To compare and correlate preoperative TMJ diagnosis based on MRI findings with the perioperative TMJ diagnosis via direct visualization of the same joints during TMJ arthroscopic procedure

Materials and methods:
85 patients were selected suffering from internal derangement of TMJ with different Wilkes classification. A total of 108 joints were subjected to first diagnostic arthroscopic TMJ lysis and lavage. Those procedures were done in Department of OMFS, Cairo University, Cairo Egypt.This study was assessed through correlating preoperative TMJ diagnosis based on MRI interpretation, to perioperative TMJ diagnosis based on arthroscopic findings.

Results of investigation:
This study revealed that Preoperative diagnosis, based on MRI assessments, came into co-ordinance with arthroscopic findings in 73 (67.51%) studied joints but were different in the remaining 35 (32.41%) joints. Ratios are significantly different between the two modalities of diagnosis, P= 0.001. It showed also a statistically significant effect of Wilkes classification on the accuracy of the preoperative MRI diagnosis when compared to the arthroscopic findings.

Conclusion:
This study concluded that the primary arthroscopic intervention has a positive effect on having accurate final TMJ diagnosis when compared to preoperative diagnosis based on MRI interpretation which is proved to have limitations.