You’re not imagining it: The Broadway musical “Groundhog Day” really has been unusually accident-prone.

Following a couple of days of doubt, Andy Karl performed in the production’s opening night performance April 17 after an onstage injury that stopped the show during a critics’ preview April 14. Soldiering on with a torn ACL, he pushed through the show with a mild limp and a big black knee brace, revealed to the audience every time his character puts on his pants at the start of the one day he lives over and over and over again. The injury came after a headline-grabbing first preview that saw the set’s turntable stop early in the night, requiring the actors to finish the show as a semi-staged concert reading.

“This is not a complex production, and it has had more glitches visited upon it than I’ve ever known on anything else I’ve ever done,” said director Matthew Warchus at the opening night afterparty at Gotham Hall. “What it makes me realize is that I’ve been amazingly lucky, and in a sense we all are. Anybody who mounts a show is dealing with a volatile cocktail of elements — hundreds, thousands of elements — and any one of them could go wrong at any time. The most remarkable thing is that they don’t. A normal production is a kind of catalog of good luck, and this has been mostly good luck with notable back luck. It’s been a mixture of emotions. There have been moments that have been infuriating, depressing.”

“Everything I’ve been doing the last 72 hours has been hour by hour,” said Karl, giving what the critics are calling a career-making performance. “Seventy-two hours ago I was not able to walk. But any pain that I felt was overridden by the love that was given to me by everybody on stage and by the audience.”

That crowd, of course, showered adoration on him throughout the performance. His injury showed itself in the occasional difficulty he had getting in and out of bed and in a running scene in which he mimed the run instead of actually doing one. In a comic seduction scene, in which a pantsless Karl tries to seduce the character played by his co-star Barrett Doss, the actor made the knee brace the chief element of his sexy-times pitch.

Throughout it all, the cast has rallied around the dictum “Champions adjust,” which Warchus first heard from the actress Kathryn Hahn when he worked with her on the 2008 revival of “Boeing-Boeing.” The director describes Doss regularly rallying the cast by crying out, “Champions!” and the cast responding, “Adjust!” “One of the cast members has had it tattooed on his chest,” he said.

Late Monday night, Karl still wasn’t sure if he’d be back onstage the next evening, saying he’d decide in consultation with a doctor. In any case, if he did go on, he felt confident that his injury wouldn’t distract from the power of the show. “This material speaks volumes,” he said. “If I’ve got a little bit of a limp, it doesn’t matter.”