Can I use voltaren (diclofenac) gel for edema?

No. Nsaids (like voltaren) can sometimes cause / contribute to edema. Try elevation / compression (snug clothing, etc.). See dr if not improving.
Maybe. If the edema (swelling) is around a small joint like the joints of the hand - then it may be effective, as the edema may be a sign of inflammation, and voltaren (diclofenac) gel is an anti-inflammatory gel. If it the edema is located over a larger joint it may be less effective.

Related Questions

I use Voltaren (diclofenac) Gel for my arthritus and tendonitus, is this an effective gel. When do Iuse it (only when I have pain)?

Yes. It is a topical anti-inflammatory that is not preventative. It can help the pain when it flares. Likewise, heat, mild stretching, massage, paraffin wax and Occupational therapy are recommended. Read more...