Rihanna ended her night at The Box nightclub in London with a cut knee after being assaulted by an aggressive man outside the exclusive nightspot.

According to eye-witnesses, the injury came after a crazed fan threw a bottle of Lucozade at Rihanna as he screamed something about her on-off boyfriend Chris Brown.

In the commotion, the singer fell against a shop shutter and grazed her knee.

The injury was deemed serious enough for her to require immediate medical attention, according to Media Take Out.

Rihanna, 24, is in UK for London Fashion Week where she presented her debut clothing collection for high street behemoth River Island.

The singer was enjoying a night of clubbing with Cara Delevingne on Saturday following her London Fashion Week debut.