Fig. 1

Synovitis within ACL-I and normal joints. Synovitis was graded within ACL-I (n = 19, 3 biopsies per individual) and normal knee joints (n = 5, 3 biopsies per individual) using the histological grading score developed by Krenn et al. (A). Individual biopsies were graded within every joint and heterogeneity was observed between biopsies locations within a given joints and also between patients (B). Three representative images of normal (C) and ACL-I (D–F) synovium presenting with no, low-, and high-grade synovitis. Scale bar equal 100 µm. *p < 0.05