The Croatian ski association says overall World Cup leader Ivica Kostelic will undergo knee surgery Monday in Basel, Switzerland, after tests showed a partial tear in his right meniscus.

Kostelic injured his knee during a winning run in a World Cup super-combined race in Russia on Sunday, and the ski association said an MRI scan conducted Monday in Croatia showed the severity of the damage.

It did not give an estimate for when Kostelic can return to skiing, but the injury is a big blow to his chances of defending the overall World Cup title.

Kostelic leads the overall standings by 70 points ahead of Beat Feuz of Switzerland, but clinched the super-combined title with Sunday's victory.