At 10.05pm on Wednesday, 18 May police were called to the Lordship Lane Recreation Ground off Higham Road, N17 following reports of an assault.
Officers attended and found a 43-year-old woman with what appeared to be slash wounds.
She was treated by London Ambulance Service and London Air Ambulance medics before being taken to an east London hospital where her condition was assessed as non-life-threatening and non-life changing.
A crime scene is in place and an investigation is underway. At this early stage there have been no arrests.
Anyone who saw or heard anything unusual or suspicious in the area around the time of the incident is urged to call 101, giving the reference 8253/18MAY.
Information can also be provided to Crimestoppers, anonymously, on 0800 555 111.