President Trump visited a combat zone for the first time on Wednesday.

On the same day, a New York Times report raised questions about the bone-spur diagnosis that helped Trump avoid military service during the Vietnam War.

Bone spurs can be painful, but are often treated with pain-relievers like Advil or Tylenol.

President Trump just got his first glimpse of life in a combat zone.

"President Trump and the First Lady traveled to Iraq late on Christmas night to visit with our troops," White House Press Secretary Sarah Sanders tweeted on Wednesday.

This marks Trump's first-ever visit to a war zone. As President, he had not previously visited a combat zone for Christmas — a traditional presidential activity during the holidays.

"He’s afraid of those situations," a former senior White House official recently told the Washington Post. "He’s afraid people want to kill him."

The visit occurred on the same day that a New York Times report raised new questions about the bone-spur diagnosis that helped Trump avoid fighting in the Vietnam War.

Trump, who graduated from the New York Military Academy boarding school, received four Vietnam War draft deferments for education during college. Then after he finished school, he received a medical exemption for bone spurs, which kept him from being eligible for the draft.

"I had a minor medical deferment for feet, for a bone spur of the foot, which was minor," Trump told ABC News in 2015 during his presidential campaign. "I was fortunate, in a sense, because I was not a believer in the Vietnam War."

According to the Times, the daughter of a man who may have served as Trump's foot doctor thinks the diagnosis was issued as a favor to Trump's father. Fred Trump owned the Queens building where the doctor's office was located.

"I know it was a favor," Elysa Braunstein, the daughter of deceased podiatrist Larry Braunstein, told the Times. She said she wasn't sure whether Trump had bone spurs at all.

"If there was anything wrong in the building, my dad would call and Trump would take care of it immediately. That was the small favor that he got," Braunstein said.

Read More: Donald Trump avoided the military draft five times, but it wasn't uncommon for young men from influential families to do so during the Vietnam War

Bone spurs form in joints, often in places where two bones meet, as a result of joint damage. Heel spurs, similarly, are "little calcifications that start to form at the bottom of the heel bone," podiatric surgeon Jacqueline Sutera previously explained to Business Insider.

The bony projections are similar to plantar fasciitis and can be especially painful first thing in the morning, when a person's feet hit the ground.

"When you're resting, the soft tissue just relaxes and there's a swelling there," Sutera said. "Then you go to stand up on it with all of your body weight, and it starts that inflammation all over again."

In general, though, bone spurs are not a debilitating condition.

"Most bone spurs cause no symptoms and can go undetected for years," the Mayo Clinic advises. "They might not require treatment."

Acetaminophen (Tylenol) and ibuprofen (Advil) are both common pain-relievers to help with the swelling from bone spurs. Some people experience no pain from spurs at all, and may never even know they have them. The American Academy of Orthopaedic Surgeons estimates that one in 10 people have foot spurs, but only about 5% of those people ever experience foot pain.

Those that do have painful spurs may opt to treat them with stretches, cortisone treatments, physical therapy, orthotics, or surgery.