'DWTS' Pro Lindsay Arnold Injured, May Not Compete Monday

Dancing with the Stars pro Lindsay Arnold has injured her knee and may be unable to compete in this week's dances with partner Jordan Fisher.

The professional dancer reportedly hurt her knee while in practice Sunday, a source told PEOPLE.

“Lindsay injured her knee during camera blocking rehearsal Sunday morning while working on a number with the troupe,” the source said.

Pro Sharna Burgess is reportedly being taught Arnold's routines in case she is too injured to perform.

“Lindsay is hopeful she’ll be cleared to dance tomorrow but it will likely be touch and go until showtime Monday,” the source continued.

In a video sent to PEOPLE, Arnold explained how she was injured.

“I was practicing the pro number and I literally just stepped up onto a stair and it felt like my whole leg gave out and stopped working and I thought it was just a one-time thing and then it happened a couple more times, just doing simple things,” she said, tearing up.

Continued Arnold, “It’s frustrating because it’s the semi finals and I want to dance it with Jordan, and I just hope this doesn’t stop me from doing that.”

Arnold is the only pro dancer still in the ballroom this season who has never taken home the Mirrorball, and she and Fisher are currently leading the pack for the season.

If Arnold is cleared to dance on Monday, she and Fisher will be dancing both a new routine a jive to “Proud Mary” by Tina Turner.