Prolonged fill in legs - possible causes?

[Kristi Schaaf <iluvdez@yahoo.com>]

After an easy 12 mile ride on Saturday, and standing
tied to the trailer Saturday night, my hubby's horse
had significant fill in all four legs on Sunday morn.
I was a little surprised because the other two horses
were fine, but I wasn't too concerned because standing
tied all night will occasionally do that to a horse.
There was no heat or pain involved whatsoever. Rain
forced us home Sunday without getting another ride in,
and I turned the horses out to pasture. It's now
Tuesday morn and that horse STILL has fill. It's not
nearly as bad (I can now see the tendon "lines"
again), but it's still not gone after over 24 hours of
being free in a pasture. Nothing else seems amiss -
still no heat or pain, no lameness, good appetite and
drinking well....I'm going to give my vet a buzz to
see if this is something I should be getting concerned
about, but I figured distance riders may know more
about this than she does! Any ideas what may be
causing this prolonged fill in a fairly fit horse?
Kristi 

=====
He's not just a horse, 
he's a little bit of
heaven on earth.

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