Randy Peterson, a longtime Des Moines Register sports columnist, owes his limp to the state of Iowa’s passion for basketball.

Moments after Iowa State defeated Iowa, 83-82, here on Dec. 10, scoring the final 9 points in a nonconference game between the cross-state rivals, a Cyclones fan belatedly running onto the court to celebrate collided with Peterson as he walked to the postgame news conference. Peterson suffered two broken bones in his lower left leg and needed surgery to implant a metal rod.

Now back to work, Peterson, who has covered Iowa sports since the 1970s, said he could not remember another season like this one.

From mid-November to mid-January, three of the state’s four Division I programs — Iowa State, Iowa and Northern Iowa — upset the top-ranked team in the Associated Press poll within the state’s borders. (Drake is the fourth Division I program in the state.) Peterson said fans were already debating where the Hawkeyes and the Cyclones would be seeded in the NCAA Tournament.

“It’s a basketball-crazy state now that the caucuses are done,” Peterson said. “As far as Iowa and Iowa State, to be as good as they are right now, at the same time, is not real common.”

The run of upsets began with unranked Northern Iowa’s stunning win over North Carolina in Cedar Falls on Nov. 21. “It’s hard for me to say it wasn’t a little bit of surprise,” said Panthers coach Ben Jacobson, who lost a second-team all-American, Seth Tuttle, and two other starters from last year’s Missouri Valley Conference tournament champions.

On Dec. 29, then-unranked Iowa downed No. 1 Michigan State 83-70 in a Big Ten Conference opener in Iowa City.

Three weeks after that, Iowa State took down Oklahoma 82-77 in a Big 12 game at a raucous Hilton Coliseum. The victory was Iowa State’s first over a No. 1 since the Hawkeyes toppled Wilt Chamberlain and Kansas in 1957.

According to research by Iowa State, the last time three Division I teams from one state defeated No. 1 opponents in a season was 1997-98, when Duke (beating Arizona), North Carolina State (North Carolina) and North Carolina (Duke) did it.

“It’s rare for all of us to all play the No. 1 team in the country the same year, let alone beat them,” Iowa coach Fran McCaffery said. “A lot of times, the reason you don’t beat No. 1 is because you don’t get to play No. 1. In our league, it’s a possibility. In Iowa State’s league, it’s a possibility. It’s harder for Northern Iowa to have that opportunity.”

Iowa, Iowa State and Northern Iowa all rely heavily on seniors, none more than the No. 4 Hawkeyes (19-4 overall, 10-1 Big Ten), who start four. Iowa has won 12 of 13 since the defeat by Iowa State, losing only at Maryland, and it overtook the No. 2 Terrapins (21-3, 10-2) for the Big Ten lead with Sunday’s 77-65 win at Illinois.

Iowa, which last won the Big Ten in 2006, is led by the dynamic 6-foot-9 forward Jarrod Uthoff, who ranks third in the Big Ten in scoring (18.4 points) and first in blocks (2.9). But McCaffery also credits a demanding nonconference schedule for preparing his team. McCaffery caught flak for a 76-74 exhibition loss to Augustana (S.D.), the top-ranked team in Division II, in early November, but he says it served a purpose, along with subsequent games against Notre Dame, Wichita State, Florida State and Marquette. Iowa has seven victories over teams in the top 50 in the Ratings Percentage Index, which should help its seeding on Selection Sunday even if it fails to win the Big Ten.

“If I feel like we have a good team and have some experienced guys, you’ve got to challenge them in every way possible,” McCaffery said. “We had four starters back. I was a little concerned because the guys we had coming off the bench are all new. I just felt like the only way we were going to get that group ready is to play this kind of schedule.”

Iowa State, now No. 14 after ranking as high as No. 2, reached a university-record four consecutive NCAA Tournaments under Fred Hoiberg, the revered Ames product known as the Mayor who left after last season to coach the Chicago Bulls. Unwilling to mess with a winning formula, his successor, Steve Prohm, consulted with Hoiberg extensively last summer and kept about 80 percent of his sets and plays.

Led by senior forward Georges Niang and junior point guard Monte Morris, the Cyclones (17-6, 6-4) remain an offensive force, leading the Big 12 with a 49.8 field goal percentage and ranking third in scoring at 82.2 points a game.

“I didn’t want to come in, rock the boat, change a bunch of stuff,” said Prohm, who was hired from Murray State. “This team had a lot of success. I had to humble myself and put my ego aside because it’s about the kids and what we can do to max this season out.”

Lately, Prohm has taken a more forceful approach. He told the players in a January meeting that this was his team now, and last week he indefinitely suspended forward Jameel McKay for an incident in practice. McKay posted an apology on his Instagram account on Sunday but has not been reinstated.

While the Cyclones and the Hawkeyes hope their best days will come in March, Northern Iowa (14-11, 6-6 MVC) will probably need to win its conference tournament to get into the NCAA Tournament this year. Jacobson, who was an assistant at Northern Iowa before being named coach in 2006, knows how special that would be in the state.

Jacobson, 45, was one of college basketball’s hot coaching prospects in 2010, when his Panthers were 30-5 and reached the NCAA Tournament’s Sweet 16 with a second-round upset of the overall No. 1 seed, Kansas. After that year’s tournament, he ran into Roy Williams, the North Carolina coach and an acquaintance from the recruiting trail, at the Portsmouth Invitational, the renowned postseason camp for draftable seniors.

Williams’ advice, according to Jacobson: Don’t change jobs primarily for money. Think about your family and what’s important to you. Stick with those, and Northern Iowa will take care of you.

Jacobson took the advice and stayed put. In 2014, Northern Iowa completed a $1 million renovation of its McLeod Center facilities. And last year the university extended Jacobson’s contract 10 years, through 2024-25, at an average salary of $900,000.

“I don’t want to age him, but it was like talking to my dad, or sitting down and having a conversation like I’ve done 100 times with my grandfather,” Jacobson, who is married with two young sons, said of Williams. “It stuck with me, and it’s proved to be exactly right.”

Still, Northern Iowa has struggled in MVC play, and with an RPI ranking of 123 will probably need the conference tournament’s automatic bid to join the Hawkeyes and the Cyclones in the NCAA Tournament.

Peterson said Cyclones and Hawkeyes fans were talking about a rematch.

“Iowa State is hosting the regional in Des Moines, so they can’t play there,” Peterson said. “If Iowa goes to Des Moines and Iowa State advances, maybe they’ll meet in the Midwest Regional in Chicago. I’m hearing a lot of buzz about that from fans. They’re already picking sides.”