A gang of about 100 teenagers pelted police with bottles and missiles during a “riot” outside a Westfield shopping centre.
It came after a weekend of violence in London which resulted in the deaths of four men.
Police said they were stepping up patrols after three men were stabbed to death and another shot dead in separate incidents.
US president Donald Trump again criticised London mayor Sadiq Khan after the violence, calling him a “disaster”.
Officers were targeted outside Westfield in Stratford, east London, after they responded to reports of a robbery.
Four officers were injured in the incident, which broke out at about 8pm on Saturday.
Three people were arrested as a result of the violence.
One woman was injured after she fell down steps to the Stratford Tube station entrance but she was not seriously hurt.
The Metropolitan Police said it had recovered a large hunting knife from the scene.
The Met Task Force posted an image of the blade on Twitter.
A police spokesperson said: "Police responding to reports of a robbery at Stratford Bus Station at 19.50hrs on Saturday, 15 June, were met with hostility by a large crowd of people.
"Around 100 members of the public threw bottles and missiles at police.
Last night U3.2 responded to urgent assistance in Stratford @MPSNewham after officers came under attack. 1 male youth attempted to make off, was subsequently detained, searched & found in possession of this hunting knife. #TSG #LethalWeapon #LivesNotKnives ^LM pic.twitter.com/SOaSGRTryU— MetTaskforce (@MetTaskforce) June 16, 2019
"A woman was injured when she fell down stairs at the tube entrance. Her injuries are not life threatening.
"Three people were arrested, two on suspicion of being in possession of an offensive weapon, one on suspicion of robbery."
A police stop and search section 60 order was put in place in the area after the violence.
It came in a weekend which saw four men killed in London in four days.
The latest victim, a man in his 40s, was found collapsed and suffering stab wounds in in Whalebone Lane in Stratford on Monday morning.
It comes after a weekend of bloodshed in the capital, which saw three other men killed in separate attacks in less than 24 hours.
The stabbing follows the deaths of two teenagers who were killed in different parts of London within minutes of each other on Friday.
An 18-year-old, named in reports as Cheyon Evans, was found stabbed on Deeside Road in Wandsworth, south-west London, at 4.42pm and died at the scene.
Two people - a 17-year-old from Merton, who cannot be named for legal reasons, and Mohammed Nadir Dafallah, 18, from Wandsworth - have been charged with murder and are due in court on Monday.
In the second incident, police were called to Hartville Road in Plumstead at 4.54pm to reports of a shooting.
The victim, Eniola Aluko, 19, from Thamesmead, south-east London, was found with critical injuries and died at the scene a short while later.
An 18-year-old man was arrested on suspicion of murder on Saturday, while three male teenagers and a 17-year-old girl who were arrested on suspicion of murder on Friday have since been bailed pending further inquiries.
On Saturday afternoon, police officers and London Ambulance Service attended reports of an injured man at Alton Street in Tower Hamlets, east London, just before 2pm.
The man, in his 30s, had been stabbed and was pronounced dead at the scene - a field next to a children's nursery and a mosque - some 40 minutes later.
Officers arrested a 33-year-old man on suspicion of murder in Victoria shortly before midnight on Saturday and a 28-year-old man was arrested on suspicion of murder in Croydon, south London, on Sunday.