Daniel Holmes for NBC News
Roseann Sdoia, who had her right leg amputated after the marathon bombing, uses a hand-cycle outside Spaulding Rehabilitation Hospital in Charlestown, Mass.
BOSTON – They've been taking their first steps, pushing through tough rehabilitation workouts and venturing into crowds again.
One month after blasts at the Boston Marathon killed three and injured 265, victims of the attack are trying to adjust to a "different normal" -- as one of them put it.
For many, that includes recovering from multiple wounds, such as severe burns, hearing loss, brain injuries and nerve and vascular damage. At least 15 have undergone amputations.
"The majority are not isolated to just having amputation but more of a complex poly-trauma," said Dr. David Crandell of Boston's Spaulding Rehabilitation Hospital, which has been treating some 30 of the wounded who require ongoing in-patient care, including most of the amputees.
Some have undergone multiple surgeries, such as brothers Paul and J.P. Norden. Others are waiting for serious injuries to heal, like Pete DiMartino, who lost 90 percent of his right Achilles' tendon and suffered multiple broken bones in his ankles. Yet others, such as Roseann Sdoia, who had an above-knee amputation on her right leg, are embarking on the next phase of their recovery by going home.
Though the contours of recovery vary among those injured in the attack, for a number of them the journey remains without end and uncertain. Even among those who kept their limbs, nerve damage can add variability to the process.
"Their ultimate outcome may not be determined for several months or even a year," said Crandell, medical director of the center's amputee program.
On various floors of the hospital, the wounded undergo exams, physical and occupational rehabilitation, or attend group or individual mental health therapy sessions.
Bartender itching to go home
One of those recovering at Spaulding is DiMartino, who pushes himself to go further in each rehabilitation session so he can go home as soon as possible.
Daniel Holmes for NBC News
Pete DiMartino, of Rochester, N.Y., suffered serious leg injuries during the bomb attack on the Boston Marathon.
The 28-year-old bartender from Rochester, N.Y., went to the marathon with friends and family to cheer on his mother, who was competing in the city's iconic road race. His left shoe was blown off in the blast.
In addition to the Achilles and ankle injuries, DiMartino suffered second-degree burns on his left leg and back, and had shrapnel buried in both legs. Doctors took muscle from his forearm to replace the skin, soft tissue and muscle he lost around his right ankle.
"The injuries he's had will probably affect the way his leg works for the rest of his life," said his doctor at Spaulding, Dr. Jeffrey Schneider, medical director of burn and trauma rehabilitation. "What he has been through is tremendous."
DiMartino arrived at Spaulding on May 2. Though he can't put weight on his right foot, he took his first steps on the left one on Friday, getting up on crutches to take an exhausting 90-second walk. He followed up on Monday by walking for two minutes, and then a third time he made it for five minutes.
"Seeing those small victories just makes me feel so much better about everything," DiMartino, whose girlfriend and older sister were also wounded, said from his hospital bed.
"It's challenging to say the least, but exhilarating at the same time," he said. "I'm advancing and I'm getting up and I'm doing these things to make my stay here shorter. … A step at a time."
On his right calf, DiMartino has a triangular-shaped contraption -- an external fixator -- with metal pins drilled into bone to stabilize the area and keep his ankle from moving. He hopes to head home -- where his sister is recovering -- in two weeks, but Schneider said the timeframe is not clear. His girlfriend is one of six people still being treated in other Boston hospitals, and the two video chat daily.
"I would really love to run the marathon next year," he said. "Every day that I'm down in the gym working out, I push myself a little bit harder than they tell me to. They tell me to do one more, I do two or three more. I know it's not a lot, but I'm just always pushing myself a little bit harder just so that I can get out of the wheelchair faster, I can get off the crutches faster ... and then I can start training."
Brothers united in recovery
Paul Norden and his older brother, J.P., went to the marathon to cheer on friends running in the race, and each lost part of a leg in the blasts.
Elise Amendola / AP
J.P. Norden, right, followed by his brother, Paul, both suffered limb-loss after the Boston Marathon bombing.
Treated at different hospitals, the close-knit brothers struggled under the separation. They were reunited, staying under the same roof, last Friday, when J.P. joined Paul at Spaulding. They shared an embrace from their wheelchairs after talking to reporters.
"It's the best thing ever, it's great," J.P., 33, said of being around Paul, 31.
"It was just so tough," Paul said of the separation. "I see him every day of my life ... it's just amazing to be back to normal."
But their joint stint at the rehab center will be short-lived. Paul, a union sheet metal worker who had his right leg amputated above the knee, will leave on Thursday to start the next phase of his recovery while J.P., an unemployed roofer who had his right leg amputated above the knee, will continue his work at Spaulding.
"We're competitive, so it stinks to see him leave," J.P. quipped, with Paul adding: "I'll visit him every day."
The brothers' doctor, Dr. Ross Zafonte, said Paul, who had been in a coma for the first five days after the attacks, was at a point where he could be a little more independent and go through outpatient training.
"His brother is not yet quite at that stage of the game," he added, "... and is undergoing a little bit more of the healing process. ... but he will get there."
Though the brothers said they'd had some bad days after the attacks, they both expressed optimism about what is to come. The pair will recuperate at their mother's home in Wakefield.
"I'm ready to move on. I feel great. It's just a different normal," Paul said. "It's exciting to know I'm going home real soon."
"It sounds weird but it's probably changed me for the better a little bit," J.P. said. "It made me realize how great people are. … so I'm happy, overall. I really am."
Old routines renewed
Outside of Spaulding on Monday, Roseann Sdoia took off on a bike that she powered with her arms. Her last in-patient day at Spaulding was Tuesday, and her occupational therapist, Samantha Geary, wanted to give her a fun rehabilitation send-off.
Daniel Holmes / for NBC News
"I have so much appreciation and gratitude for everything that everybody's done," said Roseann Sdoia, who has gone to her Boston home to continue her recovery.
The pair had already visited Sdoia's second-floor apartment in Boston's North End to test out how she will fare on one leg. And they tried out the cobblestone streets of her neighborhood with Sdoia navigating on crutches. She met a neighbor, who offered to pay for a grocery delivery service, and another greeted her with kisses.
Sdoia, who runs the residential portfolio for a development firm, has had similarly warm embraces from her friends and family, who have joined her at physical and occupational therapy, and kept a steady presence in her room to cheer her spirits.
"I have so much appreciation and gratitude for everything that everybody's done between donations and just time that ... friends have spent with me, endless hours just being here to make sure I'm not alone going through this," she said, breaking down in tears.
Sdoia admits she has had some rough days since the attacks and is not sure what to expect when she leaves the safety net of the rehabilitation center. But she figures more emotions will emerge when she departs.
"I honestly don't really know what happened to me. I mean, I know I was in a bombing, I know I lost part of my leg. I know that, but I guess I really won't know exactly what happened again until I go home, and I'm back in daily life, and dealing with getting around on the crutches and traversing ... things that aren't handicap accessible," she said. "It's going to be a challenge and I think at that point it will hit me."
She has re-started familiar routines, like watching the 10 p.m. news and tuning into the radio in the morning. Sdoia hopes she will get a prosthetic in a few weeks, which she said would be "liberating."
"So the crutches are temporary," she said, "and, in my head, so is my disability, is how I look at it."
How to help:
For a general fund to help victims, the One Fund, created by Boston's mayor and the governor of Massachusetts, is accepting donations.
To donate to individuals featured in this story, here are funds they have set up:
Heightened security, empty streets, and memorials mark the the days after the Boston Marathon bombings.
Full coverage of the Boston Marathon tragedy on NBCNews.com