"He's mostly bedridden but he's now able to get to a wheelchair and last time he was able to sit in one for three hours," Kent said.
Being in a wheelchair at a right angle puts a lot of pressure on Joel's hip joint, on which he had to have a nine-hour operation.
Kent said Joel's recovery would be a long one because he had injured both legs. If it had been just one leg he could have put weight on the other, Kent said.
The family have started a Givealittle.co.nz page to raise money for Joel's recovery because most of the costs are not covered by ACC or British social services.
They have raised more than $14,500 since the page was created on June 21 and will give any extra money to other pages.
"The kindness of everybody has been quite overwhelming and humbling," Kent said.
Once Joel leaves hospital he will need to go to a rehabilitation centre or go back to his Putney flat and have regular rehabilitation sessions to become mobile enough to fly home but this will have to be paid for privately because he is not a British citizen.
His flight home will also need to be paid for and will need to be business class because his leg will need to be elevated.
Once he gets home his rehabilitation, which is expected to take between six and 12 months, will not be covered by ACC because it happened in Britain and Joel had been out of New Zealand for more than two years.
The former Dannevirke High School student was expected to leave hospital in the next 10 or so days but would find the rehabilitation tough, his brother said.
"He's in pretty good spirits considering."
Joel had always wanted to live in London, and because his grandmother was born in England he was able to stay on a five-year visa with the right of renewal.
The 26-year-old was considering moving back once he was better because he "doesn't want to leave London on these terms", Kent said.
He had just been dropped off by an Uber to a friend's house so they could catch a taxi to the airport at 3 the next morning for a holiday in Croatia when the attack happened.
"He was in the wrong place at the wrong time."
He was assaulted and robbed by a man on his friend's doorstep but managed to get free and was pursued up on to a rail overpass.
The next thing he remembered was waking up at the bottom of some stairs.
Kent said police had CCTV footage of the offender and hoped to locate and charge the man with robbery and grievous bodily harm.
People can donate to help Joel's journey by visiting www.givealittle.co.nz/cause/getjoelbackonhisfeet.
