Phillies president Dave Dombrowski never heard of it. Neither had manager Joe Girardi or general manager Sam Fuld. The Phillies were introduced earlier this month to pseudogout -- which is when calcium crystals deposit in joints to cause pain and swelling -- when doctors were finally able to explain why Didi Gregorius’s elbow was, as the shortstop described it, red hot.

And Gregorius said he never heard of pseudogout, either.

“I heard it when they told me about it,” he said. “I’ve heard of gout, but I never heard of pseudogout. I was like ‘Yeah. OK.’ It was a little awkward and weird finding out after they did the bloodwork and stuff. Well, it’s something new.”

Gregorius rehabbed Tuesday night in Trenton with triple-A Lehigh Valley and could join the Phillies as soon as later this week. He has not played for the Phillies since May 12, when his right elbow became so swollen that he had trouble fully extending his arm.

The swelling alleviated enough earlier this month for Gregorius to begin a rehab assignment, but the elbow flared up again. And that’s when the cause of the swelling was identified.

“It [stunk] ... because people thought I just had inflammation,” Gregorius said. “Anything with throwing or hitting, it would flare back up. I couldn’t do anything. Now I’m touching my shoulder. We’re headed in the right direction. It [stunk] in the beginning not knowing what was going on.”

Both gout and pseudogout are forms of arthritis but gout is caused by a buildup of uric acid crystals and is usually found in feet.

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“I’m limited on my knowledge of the condition. I think most of us are,” Fuld said. “But it seems like it’s very manageable. It’s of relatively low concern. It’s just unique.”

The Phillies returned second baseman Jean Segura from the injured list before Tuesday’s series opener with Miami, giving them half of the middle infielders with whom they started the season. Segura and Gregorius have been together on the active roster for just five weeks.

The Phillies have replaced Gregorius at shortstop mostly with Ronald Torreyes, who entered Tuesday hitting .254 this month with a .678 OPS in his 20 games. Torreyes is a strong defender and has been a fine replacement, but the Phillies have missed Gregorius’ bat. He hit .284 last season with a .827 OPS but started this season -- the first of a two-year deal -- by hitting just .266 with a .630 OPS in 32 games.

The Phillies hope that production dip was caused by pseudogout. Gregorius is treating his condition with medicine, but he’s unsure if the issue will eventually go away or if he’ll have to manage it indefinitely. The treatment, Gregorius said, has completely removed the pain.

“It’s making progress, so hopefully it doesn’t come back because then I’ll be [ticked] off,” he said.

Tuesday night was Gregorius’ fourth rehab game in triple A since being diagnosed. He entered Tuesday with three hits in six at-bats and played seven innings on Sunday, which was a good sign as the Phillies want him to play nearly complete games on consecutive nights before they return him to the majors.

Gregorius was diagnosed in 2011 with a chronic kidney disorder. He said a doctor told him that his kidney issue has nothing to do with pseudogout. He’s still learning -- just like everyone else with the Phillies is -- about his condition. But does he know what caused it?

“I have no clue. I’m not sure. Let’s go with that,” Gregorius said. “If I start saying things, this and that, it’s going to turn into a thing.”

“Everybody seems to be aligned and on the same page now,” Fuld said. “Finally, for Didi’s sake, we can get him at the 1-yard line in creating a clear plan. It’s frustrating for him and everybody else involved. But him in particular. Whenever you get hurt, you want to have a clear path to get back. So I feel for him.”