A man was stabbed outside the stadium after violence broke out in "planned" scuffles between supporters outside Upton Park.
The trouble appeared to have been caused by fans without tickets to the game, a spokesman for the Metropolitan Police said.
He said: "It looks like there has been some planned trouble and there has been some violence outside."
Officers have made two arrests, one for disorder and the second for breaching of a banning order.
Police said the stabbing, in Priory Road close to the stadium, is connected to
the fighting and the man is being treated by paramedics.