Bruising of the hands and arms happens increasingly as we age for a number of reasons: 1) over the counter and prescription anticoagulant supplements and medications like fish oil vitamin E, aspirin, ibuprofen (and other NSAIDS), Coumadin and medicines like Plavix and Xarelto, 2) Chronic sun damage (called Solar Purpura) and 3) Age (called 'senile pupura').
Reducing anticoagulants that are not medically necessary may help - but don't stop any medication without checking with your primary physician. Products and procedures that improve the quality of the skin - gentle cleansing, moisturizing, alpha hydroxyl acids and retinoids - may reduce a small amount of the bruising but once the skin and vessels are that fragile, it is difficult to stop their formation.
However if you also have volume loss of the tops of the hands, filling them with Radiesse can both improve the hand contour and because Radiesse is a white gel, camouflage the bruises.
I hope that answer was helpful. Best wishes.