A 48-year-old woman lost control of her motorcycle near the top of the "S" turn on the Kaukonahua Road on Sunday and was seriously injured, Emergency Medical Services reported.
The incident occurred just before noon. EMS said the woman was wearing a helmet.
A Honolulu Fire Department spokesman said the woman was taking the turn and laid down the motorcycle when she lost control.
Capt. Carlton Yamada said she complained of leg pain to responders. EMS took her to the trauma center in serious condition.