APOD and osteoarthritis, knee: Apolipoprotein D (ApoD) is a member of the lipocalin family known to transport small hydrophobic ligands that occurs in the macromolecular complex with lecithin‐cholesterol acyltransferase, which was relate to the extracellular matrix and cell adhesion processes in osteoarthritis synovium, and associated with molecular heterogeneity in low‐grade knee osteoarthritis cartilage (Steinberg et al., 2021).