Marielle Thompson suffered a knee injury during a training run ©Getty Images

Reigning Olympic ski cross champion Marielle Thompson has suffered a serious knee injury during a training session, which puts her hopes of competing at Pyeongchang 2018 into major doubt. 

The world number one reportedly crashed after a jump in Saas Fee in Switzerland.

The Canadian was flown to Vancouver for an MRI scan with results showing Thompson had ruptured her anterior cruciate ligament and medial collateral ligament.

"It's definitely disappointing to hear the results after such a productive summer of training in the gym and on snow," said Thompson, according to CBC.

"I'll be making a plan with my team moving forward and when the time is right getting back on the ski cross course stronger than ever."

Marielle Thompson has reportedly ruptured her anterior cruciate ligament and medial collateral ligament ©Getty Images
Marielle Thompson has reportedly ruptured her anterior cruciate ligament and medial collateral ligament ©Getty Images

Thompson won gold at Sochi 2014 and was expected to challenge once again in South Korea.

It is the second serious knee injury the Canadian has suffered.

She also tore a meniscus in January 2015 and returned to competition 11 months later.

During last year's winter season, Thompson won seven of the 13 International Ski Federation World Cup races.