Fig. 2

Representative illustration of the histopathology of mice knees after injection of guar gum (GM) or Hylan G-F20 (HY) (100 μg/25 μL) or saline into naïve joints and analysis of histopathology scores. Knee joints were excised after 7 or 28 days and processed for hematoxylin–eosin staining. Saline-injected joints appear normal (a); there is mild synovial hyperplasia (arrow-heads) in GM and HY-injected joints at 7 days (b and c, respectively; insets); at 28 days, there is no long synovial hyperplasia with mild fibrosis in HY (d, arrow; inset) with apparently normal fat subsynovial tissue in a GM-injected joint (e, dashed arrow) (Original magnification × 200). Proliferation of synovial cells (f) and cell influx (g) into the synovia were evaluated under optical microscopy using HE and Safranin-O staining. Data are medians (IQR) of n = 6/group; *p < 0.05 using Kruskal-Wallys test