In the lower part of the hind legs (where I see swelling) there is no muscle just tendons and bones which you usually see. It does look like edema (stocking up). If it's soft and jelly like probably edema (fluid) firmer is usually inflammation/swelling. Spice stocks up even on 24/7 turnout if she isn't moving a lot.
I agree with Elana with those legs, you might have soundness issues.