Ayumi Tanimoto, the reigning women's 63-kg Olympic judo champion, was scheduled to undergo surgery on her right knee on Tuesday, sources said.
Tanimoto, who captured her second consecutive Olympic title at last summer's Beijing Games, dislocated the knee and also damaged ligaments during practice in March and could be sidelined for up to six months.
Tanimoto wrestled while still nursing the injury at the National Weight Class Invitational Championships in Fukuoka earlier this month, but she lost on points to rival Yoshie Ueno in the final.