Police were called at 4.32am on Saturday, 30 October to report of a fight on North Street in Barking.
Officers attended and found a 33-year-old man with a leg injury. He was taken to hospital by the London Ambulance Service for treatment.
A second man, aged 30, was found nearby with slash injuries that are not believed to be life-threatening. He was arrested on suspicion of causing grievous bodily harm, assault on an emergency worker and possession of Class A drugs. He was taken to an east London police station where he remains in custody.