What happened

Shares of chiropractic chain The Joint Corp. (JYNT -2.29%) jumped 15.5% through 10 a.m. EDT this morning. The primary catalyst for the move appears to be the company's announcement that its stock will join the S&P SmallCap 600 index before market open on Thursday, May 27.  

Investors are presumably rushing to buy The Joint stock now in order to "front-run" index funds and ETFs that mimic the movements of the S&P SmallCap 600. Those funds and ETFs will have to buy shares of The Joint themselves on Thursday, in order to accurately reflect the composition of the index.

Green arrow trending up over the numerals 2021

Image source: Getty Images.

So what

But that's not the only reason to be interested in The Joint stock. Earlier this month, The Joint reported earnings for its first fiscal quarter 2021.

Same-store sales jumped 21%, and total sales (from both existing and newly opened storefronts) grew 29% year over year, with net income of $0.16 per share -- nearly triple last year's Q1 total.

Now what

Excitement over The Joint stock could die down after the S&P SmallCap 600 index adjustment is made. Longer-term, though, The Joint stock could enjoy strength if management hits its goal of generating between $73.5 million and $77.5 million in revenue this year, and positive adjusted EBITDA between $11 million and $12.5 million. Wall Street believes the company could earn $0.35 per share in profit, nearly four times what the company earned in 2020.  

That could be enough to keep today's stock price rally going.