The present invention provides a method of treating a subject in need thereof comprising classifying the subject into functional group FG1, FG2 or FG3, wherein i) when the subject is classified into the FG1 functional group, (A) the level of OPN or the activity of OPN in said subject is increased; (B) the subject is not treated with a brace; or (C) a combination of (A) and (B); and ii) when the subject is classified into the FG2 or FG3 functional group, (A) the level of OPN or the activity of OPN in said subject is decreased; (B) the subject is treated with a brace; or (C) a combination of (A) and (B).