The season 25 pro, 23, performed with celebrity partner Jordan Fisher on Monday’s semifinals show, wearing a tan knee brace. Their first dance, an Argentine Tango, was to “Brother” by NEEDTOBREATHE, inspired by Fisher’s role as an older sibling to his brother Cory and sister Trinity.
Fellow pro Sharna Burgess, who was eliminated alongside her partner Derek Fisher earlier this season, was on standby in case Arnold was unable to dance.
“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,” Arnold said in the video from their practice, that was exclusively shared with PEOPLE.
In the footage, Arnold teared up during physical therapy treatment. “It’s frustrating because it’s the semifinals and I want to dance it with Jordan, and I just hope this doesn’t stop me from doing that. That scares me,” she said.
Following the show, Arnold gave reporters an update on her knee.
“It feels good when it’s in the brace, that’s why I had this [brace] on my leg tonight,” she said. “I honestly knew that I was going to dance with Jordan tonight – whatever I had to do to make it happen. I could not miss out on that. We have just one more week of dancing together and I will not let Jordan dance the finals without me.”
And after earning a 28/30 for their performance, Fisher revealed he suffered a minor injury during rehearsals on Monday. “I have a scratched cornea [due to] a nail in the eye,” he told co-host Erin Andrews.
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Fisher later told reporters after the show that “everything hurts” post-performance.
“Light hurts, blinking hurts, keeping my eyes open hurts, it’s hard to see but it’s just one of those freak things,” he said. “It’s definitely been the hardest couple of days in the competition but we’re grateful that we’ve been able to cap these couple of days off like a pirate with one good leg and one good eye still managing to make a trip to the finals.”
WATCH: Lindsay Arnold Is Injured During DWTS Rehearsals
Fisher also revealed that the eye injury is recurring.
“I’ve scratched the same cornea about 4 years ago and only about a year and a half ago did it finally get to a point – it just takes a long time to heal,” he said. “But I’m a big boy and it’s irritation more than anything and I can deal with that. I’m just so grateful that with the best partner in the entire world we have a trip to the finals and I couldn’t be more grateful to share this night with her.”
After earning a perfect score, co-host Tom Bergeron asked Arnold if she could’ve ever imagined getting three 10s following her injury. “Honestly no. I wanted to be here with Jordan,” she said.
“So grateful that it turned out we could do this together because that was the most fun I’ve had in a very long time dancing on the show. So thank you,” Arnold told Fisher.
Arnold is the only pro left in the competition who has never won the Mirrorball Trophy.
“Lindsay injured her knee during camera blocking rehearsal Sunday morning while working on a number with the troupe,” a DWTS source previously told PEOPLE on Sunday.
Violinist Lindsey Stirling suffered a rib injury two weeks ago but danced through the pain and has remained a serious contender for the show’s top prize. “It’s doing better. We still have to be careful but it’s getting better every day,” Stirling told reporters post-show.
In addition, pro Witney Carson and celebrity contestant Victoria Arlen also both revealed they suffered injuries earlier on Monday.
Dancing with the Stars airs Mondays (8 p.m. ET) on ABC.