Bah.
You can't hardly tell from this pic, but his right leg (on the left in
this pic) is swoll above the fetlock.
Now
he's reversed his legs and the non-gimpy one is in front, showing it's
normal svelteness.
My
finger is right on the knot that I can feel on the side of his leg. It's
not a hard knot - more a localised lump.
Same
leg, minus finger.
Hmm. Now I'm looking at it carefully and it looks like there's some hair missing. Wonder if he clonked himself?
Skinny
left un-gimpy leg 
Puffy
right gimpy leg
Both
legs together, standing more or less square. The gimpy one is the *clean*
one.