Police were called at approximately 9:05pm yesterday to reports of a robbery in Albion Street, Bermondsey.
The female victim informed officers that her mobile phone had been stolen by a male youth who had then fled on a bicycle.
A short while later officers detained a fifteen-year-old male youth on a bicycle in Southwark Park Road.
Whilst being detained, police say the boy “came off his bicycle”.
He was taken by the London Ambulance Service to a south London hospital, where he remains in a stable condition with facial injuries.
A statement from the Met said: “The Met’s Directorate of Professional Standards and Independent Police Complaints Commission were informed as is routine.”