Elevated serum and SF FSTL1 levels in OA patients. (A) Serum FSTL1 concentrations in HCs, OA patients, male HCs, male OA patients, female HCs and female OA patients. (B) SF FSTL1 concentrations in control trauma patients (Con), OA and RA patients, male OA patients and female OA patients. The horizontal lines represent the median values. Each point represents an individual value. Con, control trauma patients; FSTL1, follistatin-like protein 1; HC, healthy control individual; OA, osteoarthritis; RA, rheumatoid arthritis; SF, synovial fluid. **, P < 0.01; ***, P < 0.001.