if you can get Comfrey tincture, arnica tincture and witch hazel and mix them together they form what we call 'bruise juice'. Soak a pad in the juice and compress it over the knee for 15 minutes 3 times a day. It will eat away the bruising. This is a formula that is used in period reenacting for fighters (swords, etc) to get rid of bruising/swelling.
Good luck, I hope that your trip comes off as planned and I can't wait to see your trip reports!