CXCR4 and arthritic joint disease: Some examples include [68Ga]-pentixafor, a PET tracer that was originally developed for cancer imaging by binding to CXCR4, which is expressed on several proinflammatory immune cell types, or 68Ga-FAPI, which binds to the transmembrane serine protease fibroblast activation protein‐α (FAP), whose expression is high in activated stromal fibroblasts at sites of tissue remodeling and is found primarily in pathological conditions such as fibrosis, scar/granulation tissue, cancer, and arthritis [31].