Antonio was taken to hospital after his Ferrari was involved in a single car crash.
The club said in a statement today: "West Ham United can confirm Michail Antonio has undergone surgery on a lower limb fracture following a road traffic accident on Saturday afternoon.
"Michail will continue to be monitored in hospital over the coming days.
"Everyone at the Club wishes Michail a speedy recovery and wishes to express its sincere gratitude to the football family at large for the overwhelming support shown since yesterday’s news, as well as extending a heartfelt thank you to the emergency services and first responders who attended to Michail in the immediate aftermath of the incident, and the medical team who continue to aid him in his recovery.
"The Club will provide further updates when appropriate."