Since September 2021, Deion Sanders has suffered so much trouble in his left leg that he’s undergone 10 surgeries on it, with more procedures apparently coming later.

Doctors already had cut out both sides of his left calf and amputated two of his toes in 2021. Then on Friday, they removed a “really bad” blood clot in his thigh, along with a number of smaller clots below the knee.

Sanders, 55, once was one of the fastest players in the NFL. But now he faces new questions about his health and mobility as the new head football coach at Colorado.

To learn more about what he might be facing, USA TODAY Sports talked to doctors who are not treating Sanders personally but agreed to discuss in general the conditions that Sanders and his doctors have revealed publicly. Sanders also revealed more information Saturday after his surgery Friday near Denver.

How serious is Deion Sanders' condition after latest surgery? And how will it impact his future?

It's no minor health issue. In interviews after his previous surgeries, he said his family has a history of blood clots, including an uncle who died as a result. Sanders even said he nearly died himself when he spent 23 days in the hospital fighting them.

“Any time you’re losing circulation, it’s very serious,” said Robert Brodsky, president of the American Society of Hematology and professor of medicine at Johns Hopkins University.

What is the main issue?

Sanders and his doctors have described circulation problems in his arteries, which carry blood away from the heart, as opposed to his veins, which carry it back. Almost all of his issues have involved his left leg, though he said in a video posted Saturday by his son Deion Jr. that he also has a clot in his right thigh that will be removed soon. Sanders has described his issues as blood clots, which block or narrow the passage of blood through the arteries.

“The arteries take oxygenated blood from the heart and deliver it to the tissues, so if the conduit to get to the tissue is blocked, you lose the blood supply, and that portion below where that clot is will die from not getting enough oxygen,” Brodsky said.

Sanders, who was hired at Colorado in early December, said Saturday he expected to leave the hospital Sunday, but his girlfriend, Tracey Edmonds, indicated he was released a day later.

“Thank you Lord for strengthening #CoachPrime @deionsanders so that he could leave the hospital today and be home tonight to rest and recover in his own bed!” Edmonds wrote on Instagram Monday.

When did this start and why?

In 2021, when Sanders was the head coach at Jackson State in Mississippi, he underwent surgery to repair an inflamed nerve and dislocated toe on his left foot – injuries that stemmed from his career in the NFL. About two weeks later, he said his athletic trainer urged him to get medical help when she saw two of his toes had turned unusually dark. Doctors said he had femoral arterial blood clots, which led to compartment syndrome and another round of surgeries and amputation.

Last December, he said in an interview with former NFL player Shannon Sharpe that he had nine surgeries in this period, that his life was at risk at one point and that he almost needed his leg amputated below the knee.

He missed three games that season as a result. But he returned to the sideline in a wheelchair and was left with a leg that was narrowed at the bottom. Tissue had been cut from both sides of his calf to relieve fluid buildup. His big toe and the toe next to it also were removed.

How does that relate to his current state?

Sanders, a Pro Football Hall of Famer, has said he has been taking blood thinners and other medication but said he has no feeling at the bottom of that foot and walks with a limp. Two of his remaining toes are abnormally bent hammertoes that he wants to “straighten out” with additional procedures. But he said he first needed surgery on a clot in his left thigh to improve his blood flow downstream to the foot.

“Ordinarily, you have three arteries that are putting blood to your foot,” doctor Ken Hunt told Sanders before his latest surgery, as documented by Thee Pregame Show, one of Sanders’ favored YouTube channels. “After the procedures you had before, now it went down to one. And that one was a little bit tenuous.”

What about his thigh?

In the same video with Sanders before his recent surgery, another one of Sanders’ doctors, Donald Jacobs, mentioned “clotting from an aneurysm.” Aneurysms can happen in the leg and create enlarged blood vessels.

“Arteries are supposed to be this big and round in your groin, and it’s, you know, that big and round,” Jacobs told Sanders as he used his fingers to portray a larger artery. “If that gets bigger… that’s not life-threatening necessarily, but it’s a major operation to replace the artery with a bypass."

In the same video before surgery, Jacobs, a vascular surgeon, explained to Sanders that when blood coming out of a larger artery goes into a smaller one, it slows down and can clot. “If it’s going slow enough, it clots,” he said.

It’s not clear whether that’s the kind of surgery Sanders had Friday. His doctors are not doing additional interviews about it, according to a spokesperson with the hospital.

After the surgery Friday, Sanders said in the video posted by his son that the clot removed from his left thigh was “really bad” and was “doing the most damage.” He said other smaller ones were removed from below the knee. The one in the right thigh “is not as bad as the other one, but they want to get it before it grows," Sanders said.

Is it genetic or something else?

Sanders said in his interview with Sharpe in December that medical professionals asked him if his family had a history of blood clotting. He said his mother told him one uncle died from such complications, another one almost did and that his mother also had it.

Some genetic factors can contribute to clotting, experts said. But it’s not clear that is related to his current situation or what type of clots his family members had. Surgery itself can lead to clotting, but the risk of not doing surgery and losing a limb can outweigh that risk.

What is his outlook?

It depends on his recovery, but Sanders indicated he could have more surgeries to help his foot and toes and another one to remove the clot in his right thigh.

In general, a patient who has an arterial clotting problem and surgeries to resolve it can be left with damaged or blocked arteries, “which can be a long-term problem,” said vascular surgeon Richard Denney, who works at the UCHealth Medical Center of the Rockies in Loveland, Colorado, but is not involved in Sanders’ case. “Arteries that are completely blocked are difficult to get back open when it’s outside the acute phase.”

In Sanders’ case, some arteries to his foot have essentially shut down, according to his doctors. Jacobs, the vascular surgeon, said earlier this month Sanders could lose his foot, depending on how things develop. Sanders himself later downplayed that risk as a worst-case scenario.

But with only two months to go before Colorado opens the season on Sept. 2 at TCU, it’s not clear how many more surgeries he’ll undergo before then or how mobile he’ll be on the sideline without help. After Colorado’s spring game in April, he talked about shoes being built to “make sure I could get through the fourth quarter.”

The situation since then has gotten more complicated.

“The fact that they’re having to continue to do it and move up the leg says that the problem is still going on,” said Brodsky of Johns Hopkins, who is not involved in Sanders’ case. “It’s not acutely life-threatening, these things, but what happens with these is sometimes it just keeps progressing up the leg.”

Follow reporter Brent Schrotenboer @Schrotenboer. Email: bschrotenb@usatoday.com

This article originally appeared on USA TODAY: Deion Sanders and blood clots: What we know