You can differentiate between ionic, covalent and molecular compounds by the fact that ionic compounds contain elements that include both a metal and a nonmetal. Molecular compounds contain both non metals covalently bonded to each other. While acids most often on their chemical formula start with the element of Hydrogen - H.
For Eg - sulphuric acid
H2SO4
hydrochloric acid - HCl.
It is true it is used for inflammation and pain in muscle and joints it is also used for muscle and bone disorders