IMMUNOHISTOLOGIC ANALYSIS OF SYNOVIUM IN INFRAPATELLAR FAT PAD AFTER ANTERIOR CRUCIATE LIGAMENT INJURY

To clarify the natural course of synovitis after anterior cruciate lig ament injury, we took synovial tissues at various periods after injury and analyzed them immunohistologically. Twelve patients with isolated anterior cruciate ligament injuries participated in the study. Inflam mation intensity was graded semiquantitatively based on the following parameters: :synovial lining cell depth, synovial hyperplasia, vascula r hyperplasia, lymphocyte infiltration, and the expression of cell adh esion molecules. The expression of fibrogenic cytokines and the degree of fibrosis were also investigated to elucidate the mechanisms of art hrofibrosis. The results demonstrated that synovitis in the infrapatel lar fat pad subsides within 3 months after injury with the progression of fibrosis. Fibrogenic cytokines, platelet-derived growth factor and transforming growth factor-p, were detected at fibrotic sites, sugges ting their involvement in arthrofibrosis. An increased incidence of ar throfibrosis recently has been recognized to occur when anterior cruci ate ligament reconstruction is performed within several weeks after in jury. We speculate that when anterior cruciate ligament reconstruction is performed during the stage of acute synovitis, the operation may f urther promote the synovitis, accelerating the arthrofibrotic reaction . Waiting to perform the anterior cruciate ligament reconstruction unt il the synovitis resolves may possibly decrease the motion problems se en postoperatively.