  Let f be a nondegenerate quadratic form in at least 5 variables over a number
field K and let S be a finite set of valuations of K containing all Archimedean
ones. We prove that if the Witt index of f is at least 2 or it is 1 and S
contains a non-Archimedean valuation, then the S-arithmetic subgroups of the
special orthogonal group of f have bounded generation. These groups provide a
series of examples of boundedly generated S-arithmetic groups in isotropic, but
not quasi-split, algebraic groups.
