RESUMO
The etiology of posttraumatic arthritis has not been studied well. Although it has long been assumed that articular incongruity leads to post traumatic arthritis, clinical and basic sciences evidence to support such claim are not sufficient. On the other hand, the relationship of instability due to anterior cruciate ligament deficiency and Arthrosis has not been clearly defined and the relative importance of instability and incongruity is unknown. ACL tearing were created in right knees of 9 rabbits [group A] and ACL tearing and displaced lateral condylar fracture with 1 mm step were created in another 9 rabbits [group B]. After 6 months, osteoarthritis changes were compared between control knee and injured knee of each rabbit and between the two groups. In both groups, osteoarthritis changes in injured knees were more comparing to the control knee and in whole osteoarthritis changes were significantly more in group B compared to group A. The unstable knee due to ACL deficiency goes toward osteoarthritis faster than normal knee. Incongruity in unstable joint increases intensity of osteoarthritis changes. It shows the importance of achieving anatomic reduction in intra articular fractures before ligament reconstruction