The incident happened in Woolwich New Road just before 9.40pm yesterday (May 30).
Officers and London Ambulance Service crews attended and found a man with injuries to his arm.
He was taken to hospital where he his condition was assessed as non life-threatening.
A man was arrested on suspicion of affray and remains in police custody.
A spokesperson for Metropolitan Police said: “Police were called at 21:41hrs on Friday, 30 May to Woolwich New Road, SE18 following reports of two men fighting.
“Officers attended and a man was located with injuries to his arm.
“He was taken to hospital where he remains. His injuries are not believed to be life-threatening.
“A man was arrested on suspicion of affray and remains in custody.”
