Welcome to Flyertalk Hinda50. I flew from Los Angeles to Washington, D.C. about 6 weeks after having a total knee replacement. The most important thing is elevating the injured legs. So, first class with a good recline and foot rest is important. If FC is not practical, consider a bulkhead which has enough room to prop his legs on a bag or box. In my case I decided it was worth the expense to travel on Virgin America First Class. The small FC cabin is very comfortable and the seats recline well enough to prop the leg on the foot rest. Flight attendants are very accommodating. Good luck.