  We investigate the spin alignment of vector mesons arising from locally
polarized quarks and anti-quarks (local spin alignment) in heavy-ion
collisions. We find that $\rho_{00}\neq 1/3$ does not necessarily signal the
global polarization of quarks and anti-quarks along the orbital angular
momentum of the system, but may also originate from their local spin
polarization. Such local spin polarization could be induced by local vorticity
arising from the anisotropic expansion of the fireball. We further propose
experimental observables that can distinguish between the local and the global
spin alignments. Measurements of these observables in heavy-ion collisions can
probe the vorticity pattern and shed light on the puzzles of $\phi$ and
$K^{*0}$ spin alignments.
