Recently, LHAASO has performed precise measurements of
the all-particle spectrum, the mean logarithmic mass and the proton
spectrum of cosmic rays at energies around the knee with
more elemental spectra expected in the near future. These datasets
for the first time bridge direct and indirect measurements
and provide an unprecedented opportunity to test models of
CR acceleration and propagation in the Galaxy.
In this work, we develop a phenomenological model of CR spectrum
and composition, in which CRs experience rigidity-dependent
effects during their propagation in the Galaxy.
We conclusively find that a single population of sources
with propagation effects can't plausibly explain both elemental
and all-particle spectra around the knee. In contrast,
a two-population model that includes an additional
light contribution at the knee provides a consistent
description of both. We find that model requires
a relatively high but plausible energy scale shift
of $\sim15\%$ for LHAASO.