It was the hip all along.

Discomfort in Mike Lowell’s surgically repaired right hip resulted in the corner infielder heading to the disabled list on Thursday. The move represented the latest derailment by the joint to the four-time All-Star’s 2010 season, but by no means the most dramatic.

According to multiple baseball sources with knowledge of the negotiations, it was concerns about Lowell’s hip -- and not his right thumb -- that led to the unraveling of the offseason deal that would have sent him to the Texas Rangers.

While Lowell did require surgery to repair the radial collateral ligament of his right thumb (something discovered only after the Sox and Rangers had agreed to a deal that would have sent Lowell to Texas for catcher Max Ramirez), that procedure was considered fairly routine.

The medical concerns of the Rangers -- as well as multiple clubs that evaluated Lowell as a trade candidate both this spring and during the season -- focused on the notion that his right hip would impair both his availability and productivity. In some major league corners, Lowell’s trip to the disabled list will be viewed as validation of those concerns. To the Rangers and other teams, according to the baseball sources, the thumb was a relative non-issue in determining whether it was worth acquiring the player.

While Lowell had maintained that his hip felt much better this year than it did last (following surgery to repair his hip labrum in Oct. 2008), he noticed on Tuesday that the joint was “barking” and worried that it was impacting his swing. He told reporters that he was “embarrassed” when Rockies shortstop Clint Barmes made a diving play on a liner he hit on Tuesday and then had time to get up and throw him out by a number of steps for the final out of the game.

Certainly, his trip to the 15-day disabled list for what is being called a strained right hip will do little to ease any health concerns of teams that represented possible trade destinations for Lowell. That fact was one of which the 36-year-old -- who is hitting .213 with a .308 OBP and .658 OPS this year -- was painfully aware.

“I don’t think [going on the D.L.] helps my cause but I don’t think there’s a team out there that says, we’re getting this guy the way he was in 2004. I think that’s pretty realistic,” Lowell told reporters. “I’d rather not go to another team and then have them think they’re getting something and then say my hip hurts the first week. I think that would make me look bad and they’re getting something that they didn’t expect.

“That was part of the reason why I wanted to tell [manager Terry Francona about the hip injury] because I don’t really know what talks are going on but if they are, I don’t want to look like the guy that’s being dishonest. If it affects it, it affects it. I’d still rather go this route. I think it’s the right one.”   

Earlier this week, Lowell expressed uncertainty whether it was the thumb or another issue that caused the offseason deal to the Rangers to unravel.

“[Texas] might have not had a problem at all with the thumb. It might have been they wanted to make the Red Sox swallow more money. I have no idea,” said Lowell. “They might have had a problem with my hip. I don’t know. That part, I really can’t answer.”

That said, Lowell did suggest that the timeframe for treatment of his thumb impacted his 2010 season in another crucial way. After seeing comments from Red Sox team medical director Dr. Thomas Gill suggesting that an MRI would have not have affected the treatment of his thumb injury, the infielder identified his areas of disagreement with that assessment.

At the time of his injury, which occurred on Oct. 2, when Lowell fouled off a pitch against Cleveland hurler Jeremy Sowers, he received an X-ray and a physical exam. The Sox made a determination that there was a sprain -- meaning some degree of tear -- in the radial collateral ligament on the outside of his right thumb. (The radial collateral ligament is considered less important for baseball activities than the ulnar collateral ligament on the inside of the thumb, which is required for squeezing a bat or a glove.)

Lowell’s thumb was taped for the playoffs, with the expectation that six weeks of rest after the season would allow him to heal without surgery. The Sox preferred a conservative course of treatment, believing that the vast majority of radial collateral ligament injuries (more than 90 percent) can heal on their own. The team felt that an MRI would not have been useful for determining how to treat the injury, since even if it had revealed a tear, the club would have recommended waiting to see if the thumb had healed on its own.

That course is not inconsistent with a normal one in treating such an injury, according to Dr. Keith Segalman of the Curtis National Hand Center. Segalman noted that radial collateral ligament injuries are difficult to diagnose, but that the best test does not necessarily include an MRI.

“The best diagnostic test is an experienced hand surgeon examining the patient and looking at an X-ray. … An MRI can be helpful, but it’s not always definitive if you want to make that diagnosis,” said Segalman. “The big determinant about whether the ligament is completely torn or not is based on a physical exam rather than an MRI.

“The physical exam will use a regular X-ray, and on the X-ray you can see whether there’s been subluxation of the joint, meaning that the joint has shifted. If you have a subluxation, then almost universally you have a complete tear of the ligament. If you have a complete tear, we would recommend a repair [surgery].”

That said, Segalman -- who was speaking generally, and not about Lowell’s specific case -- suggested that it would be fairly routine to give an athlete an MRI either at the conclusion of the season or if the injury had not improved significantly after several weeks of rest.

Lowell, however, feels that his opportunity to prove that he was healthy to other clubs this spring was impaired by the timing of his MRI and subsequent surgery. He suggested that when he did receive an MRI from a specialist -- Dr. Donald Sheridan in Arizona, who examined him after the trade to the Rangers had been agreed upon, more than 10 weeks after the initial injury -- a nearly compete tear was diagnosed and surgery was prescribed almost immediately.

“When I saw the hand specialist in Arizona, he read the results of the MRI, and with his manipulating of the joint, he told me, I need surgery,” said Lowell. “The simple facts remains that post-MRI [in mid-December, just after the Sox and Rangers agreed to the trade], it was diagnosed within 48 hours that I was needing surgery, so obviously the MRI that proved there needed to be a more drastic next step.”

“The MRI gives a much more extensive picture, what type of tear, and obviously we know now that my type of tear needed surgery to heel it. This is no knock on Tom Gill. I don’t think any doctor in the world without an MRI would know what percentage of a tear you have, unless they have X-Ray vision.”

He believes that an MRI at any of a few different points -- at the time of the injury, after the Sox were eliminated from the playoffs or at the time that his injury was re-examined by a team trainer during the offseason, roughly six weeks after the end of the year -- would have resulted in a determination that there was a near-complete tear of his radial collateral ligament and that surgery was necessary.

The earlier that Lowell underwent surgery on the thumb, the more normal an offseason routine he would have been able to follow. Given that the recovery time from the surgery was eight weeks, he suggested that surgery by late-October or early-November would have allowed him to start swinging shortly in early January, as is his typical pattern.

However, he suggested that by virtue of the fact that because he did not receive an MRI or see a hand specialist until mid-December, roughly 10-11 weeks after the initial injury, he did not have the surgery until the last week of December. That left him unable to swing until roughly the start of spring training. That, in turn, contributed in him being unready for games until March 14, about 10 days after Grapefruit League games had begun.

Because he was not able to play until that point, Lowell contends that his opportunity to prove that he could be a healthy and productive player in the spring -- to the Sox and to other clubs -- was impacted negatively.

“The best way to put it was the timing just was not very good,” Lowell said last week. “Before opening day, I usually have 12 weeks [of swinging] under my belt where I’m finding out what’s working and fine-tuning what I want to do. I think that was a major setback for that preparation because whether Adrian Beltre had been signed or anything, whether it was to help this team or any other team, I just was unable to, because of the time, to show anyone with the number of at bats in the spring.

“I just started swinging at the end of the first week of the spring, but before you feel like you’re into that mode, we were in the fourth week of the spring, so we had 12-days left,” Lowell added. “I don’t think most teams feared at the time that the thumb was going to be an issue, but it’s hard to state that is not going to be an issue when you don’t see it, there’s no proof. I thought I had very limited at bats in the spring and if anything, I thought I was swinging the bats great at the end of spring, but, how much stock do you put into that? It’s hard.”

That said, it is difficult to discern the precise nature of the impact. The Sox might restricted Lowell's activities during spring training not just because of the thumb, but also due to limitations from the hip.

According to Segalman, had there been a diagnosis of a near-total tear for an athlete during the season, he would tend to recommend immediate surgery once the player’s season was done.

“If there’s only a month left in the season, you’d say, ‘Go ahead and play with the pain if you can tolerate it,’” said Segalman. “Then, as soon as the season is over, give him a day or two to relax, give him a good [physical] exam on the thumb and say, ‘You have a 95 percent tear. It’s not likely to heal. This is unstable. You’re better off having it fixed.’ That’s the scenario I would present.”

But Segalman also noted that an MRI shortly after the occurrence of the injury might not have revealed the problem due to the presence of inflammation and scar tissue.

Had Lowell’s tear been diagnosed by an MRI six weeks after the end of the season -- around the time that he was visited in South Florida by a team trainer, around Thanksgiving -- then it likely still would have taken a couple weeks for his surgery to be scheduled, meaning that the timetable for his return would have been altered only slightly.

Even had a near-complete tear been seen by an MRI the day after the season ended, the Sox and player might have opted to follow a conservative course of seeing whether rest would have permitted the injury to heal.

Of course, all of that is now past. The thumb is no longer a concern for Lowell, and is not an impediment to his ability to take the field.

But with his hip now sidelining him for at least the next two weeks, Lowell has reconciled himself to the reality that he will not be a major league regular any time soon. The hopes he had entering the year of finding a regular role -- whether with the Sox or, more likely, another team -- have dwindled, and so Lowell is holding out hope that he may be able to make any limited contribution a meaningful one going forward this year.

“At this point of the season, I don’t think there’s any scenario where I can reach the point where I can put up the numbers that I expected to put up,” he told reporters. “If I don’t get traded, and we reach the postseason, one at-bat could be the difference in the game. That could be satisfying in itself.”