Humana Inc.’s stock HUM tumbled 14% Wednesday, swept up in the downdraft created by UnitedHealth Group Inc.’s UNH disclosure that its senior clients are catching up on hip and knee surgeries that were delayed by the COVID pandemic, boosting costs for insurers. The stock led S&P 500 decliners, as Oppenheimer said if the trend is widespread, Humana may be most exposed as it it has a larger Medicare Advantage presence. Analysts noted, however, that Humana has not commented of late and that peers have also not drawn attention to pressure on their businesses. Other health insurers also fell with Cigna Inc. CI down 5% and…