Fig. 4

Hematoxylin/Eosin staining of representative 3-month, 12-month, 5.5-month ACLT Sham right and left tibial joints. Normal synovium is depicted with subintimal capillaries and 1-2 cell layers of synoviocytes in the 3-month joint. Surface fibrin is shown in the 12-month synovium (black arrow). Synovial hyperplasia is seen in the white arrow in the left 5.5 month joint as well as increased fibrosis of the subintimal layer (black arrow). The right 5.5-month joint has marked synovitis as pointed (white arrow) with leukocyte infiltration. The left sham knee has beginnings of fibrosis (black arrow), but no hyperplasia, and the right sham knee has scattered villous hyperplasia (black arrow). (Original magnification, × 100)