Officers also continue to appeal for witnesses and information about the stabbing.
He was taken to the hospital for treatment; his condition is now serious but stable.
Detectives from the Met’s East Area CID are investigating.
Witnesses or anyone with information are asked to call 101 or tweet @MetCC and quote CAD 4545/24Sep. To remain anonymous, please contact the independent charity Crimestoppers on 0800 555 111.
Hard calls save lives. Are you close to someone on the fringes of knife crime? Do the right thing, please give information, 100 per cent anonymously, through the independent charity Crimestoppers.
Crimestoppers never ask your name and they cannot trace your call, your IP address or the device you use. Fill in their quick online form or call 0800 555 111. It could save a life.