  We propose that the knots of the large-scale jets in powerful radio sources
represent moving and separate portions of the jet matter, with the excess
kinetic power. This can explain many morphological properties of quasar jets -
like high knot-to-interknot brightness contrasts, frequency-independent knot
profiles and almost universal extents of the knot regions - independently of
the exact emission mechanisms responsible for producing broad-band jet
emission. We briefly discuss a possible connection between this scenario and
the idea of highly modulated/intermittent activity of the jet engine.
