The star eight-year-old is hot favourite for the two-mile championship, but was reported to be lame on Monday morning due to pus in his foot.
However, specialist treatment and hard work by Henderson's team appears to have worked and the Seven Barrows trainer reports his charge to be fit for action
"Monday was horrible all round, but luckily he was sound this morning," Henderson told ITV Racing.
"We've taken the shoe back off again and put a poultice on. The farriers have done a great job and hopefully he'll be all right for tomorrow."
Altior has won at the last two Festivals but the season has not gone to plan, as he only returned to action in February after having a wind operation.
"He was ready to have his first run in the Tingle Creek, then suddenly we heard a peculiar little noise which required attention," said Henderson.
"He had that done and he has come back. He didn't have a lot of work before Newbury, the one thing was his weight was surprisingly close to his racing weight last year.
"He was fit going into the operation and he had five weeks box rest. At Newbury he was very good, but he has class. His work has been good and he has schooled great.
"At Newbury I didn't want to do it in soft ground, but it has proved that he is still a good horse in soft ground, although he is a better horse on better ground.
"Having had the race under his belt, he hasn't had to do a whole heap of work. For a horse that has had a wind operation, he is a clean-winded horse and he is very straightforward on that front.
"He is stepping towards the biggest shoes I've ever come across (Sprinter Sacre) and he has done absolutely nothing wrong so far.
"What Altior has done is remain unbeaten over hurdles and his novice chase career, and now he has to win this and finish this year as champion, but then he is still not there either.
"He is going the right way and he has got a lot of natural ability, but he has got to do it all again."