In 2011, the association conducted an internal probe that implicated 14 wrestlers and elders of the sport in rigged bouts, taking the unprecedented step of cancelling the tournament in Osaka.
But arguably the single most damaging incident was the death of a 17-year-old wrestler in June 2007.
Takashi Saito was admitted to a hospital in Nagoya with severe bruising that his fellow wrestlers and stable master, Junichi Futatsuryu, claimed was the result of a training accident. Wrestling as Tokitaizan, the boy died and an autopsy subsequently showed that his injuries were not consistent with an accident.
Futatsuryu and three wrestlers were arrested after police learned that Mr Saito had tried to run away from the stable because he found the systematic hazing and physical demands of the training too tough. Caught by his fellow "rikishi," he was taken before Futatsuryu and beaten around the head with a beer bottle. The stable master then ordered the other wrestlers to continue the assault, using a metal baseball bat on Mr Saito.