I had knee surgery a couple of years ago, and my pain was also 10 out of 10 and the only medication that seemed to work was Demoral. The swelling in the foot was probably due to not keeping it elevated.
does he ice and elevate his knee constantly? the reason his foot is swollen is probably because he didnt keep it elevated. the saying goes "put your toes above your nose" when he got his surgery did the doc give him pain meds? if not go back to a physician of clinic and tell them your situation to get some stronger pain relievers.
hope this could help.
Kathy Plunk M.D.