I am sitting under a rough wood shelter, in the midst of a Virginia thunderstorm, surrounded by three-legged dogs, watching the lightning flash ever closer. Frankie, the coonhound, starts howling. Adelaide, the husky, joins in. “It’s fine,” says Jim Nelson, co-founder and president of the Tripawds Foundation. “If anything, it’s going to hit that transformer over there.” He waves vaguely behind me. At his feet, his dog Wyatt Ray (three legs, face covered by a fabric calming cap to distract him from the storm) seems unperturbed. How the hell did I wind up here?

Like so many of my adventures, this one begins with Meg, the raggedy, red-haired mutt who was handed to me by a stranger in a London churchyard, seven years ago: “I’ll give you £100 if you’ll take this bloody animal and keep her.” I took her lead and took her home. (No, I didn’t take the money.)

Meg was trouble from the start. Unhousetrained, unpredictable and with a tendency to suddenly turn and bite, in the space of six months, she had got me arrested, been rescued by the fire brigade, knocked a child off his scooter, and locked herself in the car. I fell in love with her, obviously: there was nothing else to do. Then, one day, as she was running on grass, Meg fractured her elbow catastrophically. For three years, we battled to save her leg. Amputation was not an option. Then it was. Vets disagreed. The euthanasia needle hovered. Desperately Googling at 3am, I came upon tripawds.com, the leading online community for owners of three-legged pets. “ADVICE URGENTLY NEEDED,” I typed. “IS AMPUTATION A VIABLE OPTION, PLEASE HELP!!!” I pressed submit and off the message went, like a flare from a sinking ship.

Facebook Twitter Pinterest Sally Holladay with Frankie and Merry Myrtle. Photograph: Jared Soares/The Guardian

Eighteen months later, one leg down, but very much alive, Meg has been left at home with my mother while I have come here, to Richmond, Virginia, on a pilgrimage to finally meet the people who helped save her life. Tripawds.com is used by more than 13,000 “pawrents” of three-legged dogs and cats (plus Uno, a one-legged chicken) and this two-day convention brings together members from across the US, from Germany and the UK (me), most of whom have not met in person, though they may have talked daily for years. To get here I flew to Washington DC, zigzagged down the freeway with Alison (username: Mom2Shelby) and Jasper, her lettuce-eating dog from LA, and with Tina Schröder, whose dog lost the same leg as Meg. On my chest is a sticker with my avatar picture (Meg’s face, looking crafty, her tongue hanging out) and my username, Megstamum. As people walk past, I peer through the gloom, trying to make out their stickers. I recognise an avatar picture: Ted, a yellow labrador mix, craning around the front car seat to look ahead down the road. It’s MySweetTed, also known as Wanda. Ted died from cancer six months ago. Today Wanda, from nearby Charlottesville, is accompanied by Joe, a lively, young black fully-legged labrador, who gets sharply reprimanded by a three-legged greyhound. Age trumps legs, it seems.

Many have been rescued from abuse or neglect. Yet they sit around, some sporting party hats, waiting patiently

There are many different paths to Tripawds, but the most common is a diagnosis of osteosarcoma, a highly aggressive form of bone cancer for which amputation offers not a cure but extended life expectancy and a cessation of pain. It was this diagnosis in their German shepherd mix, Jerry, that led Jim Nelson and his wife Rene Agredano to sell their design business and home in northern California, buy a giant trailer and take to the road to make the most of whatever time they had left with their dog. “I made this promise to Jerry: stick around and I’m going to take you on the best trip in the world,” says Jim.

The website began as a blog to keep family and friends updated. The first post, written from Jerry’s point of view, and entitled simply Ouch, dates from November 2006: “I’ve got stitches in my shoulder from where the very nice doctors and students took a biopsy from my scapula bone.” Soon Rene and Jim began to get emails from people in similar situations, looking for information and support. “The animals bounce back, but the people are left with a three-legged dog and a discharge sheet, saying, ‘What do I do now?’ ” says Jim. For Rene and Jim, who are now in their 40s, the answer was to make the most of every day. “Jerry wasn’t afraid of what was to come,” says Rene, “that was us.” They vowed to “Be More Dog,” and this, in turn has become the Tripawds motto.

Facebook Twitter Pinterest Tripawds founders Jim Nelson and Rene Agredano with Wyatt Ray. Photograph: Jared Soares/The Guardian

By the time Jerry died, late in 2008, the website had greatly expanded. As well as a wealth of information on all aspects of the three-legged life, there are discussion forums, a chatroom, and more than a thousand member blogs, many of them detailing a dog or cat’s “amputation journey” (the Tripawds lexicon, “Pawesome!”, can take time for a Brit to adapt to). All this is still run by Rene and Jim from their trailer. “It was supposed to be a year-long trip,” says Jim, “but we just kept going.”

The Tripawds Foundation was established in 2011, offering a helpline and financial assistance for those in need – to help with amputation costs, reimbursement for the cost of adopting a tripawd, for special equipment and for rehab (though several of these schemes are available only to US members). Discussion forums are grouped by topic: Presentation And Diagnosis; Eating Healthy; Hopping Around. There are pictures immediately following amputation, so new pawrents can prepare themselves. “Don’t even look,” is the usual advice. “Just focus on their eyes, and on how happy they are to see you.”

For my own Meg, losing her leg appeared to be a relief as much as anything. Three days after her surgery, she came hopping out of the hospital, tail stump wagging, and never looked back. But many dogs, especially larger breeds, can take a few weeks to find their balance and adjust to the three-legged gait. For Meg, the most remarkable thing is how little the loss of her leg impacts her. Her walks are shorter but she enjoys them every bit as much. She still swims and chases squirrels. One unexpected bonus is that people tend to attribute problematic behaviour (kicking off at border terriers, for example) to her three-legged status. “Poor dog,” they say. I feel it would be disloyal of me to let on.

Facebook Twitter Pinterest A bone-shaped cake for the dogs. Photograph: Jared Soares/The Guardian

But for those fighting cancer, amputation is often just the start of an uncertain journey, full of impossible decisions. Chemo or no chemo? X-ray or not? Is it even right to amputate, when the dog may have only a few months left? A lucky few, on the other hand, will live for a number of years. Tina (username: Tinsch) has come to Virginia from Hamburg to meet “the only other people who understand what going through this means”. Her Greek rescue dog Manni lost a leg to osteosarcoma 17 months ago and is still enjoying a great quality of life: camping trips, bike rides in the forest, all from the comfort of his trailer, the ManniMobile. But Tina worries constantly. “It was the right decision for him, and I would do it again, but really it has made my life hell.” Paula Ehlers (Dobemom) describes her dog, Nitro, who has just celebrated his three-year ampuversary, as “the ultimate warrior”. “He has taught me so much – grace, dignity, strength, joy of life.”

Facebook Twitter Pinterest Clare Allan’s dog, Meg, who fractured her elbow. Photograph: Clare Allan

The storm has passed over. Karma Bevelhimer (Karma is her real and username: she’s the daughter of Colorado hippies) is cutting into a giant, bone-shaped cake, and serving it to the dogs in paper bowls. A beautiful red cardinal perches hopefully on the rail behind. I am amazed by how well the dogs behave. Many have been rescued from abuse or neglect. Several, including Wyatt Ray, lost legs after being tied up in a yard when the leash got wrapped round a limb. Yet they sit around, some sporting party hats, waiting patiently. Karma came to Tripawds four years ago, when her crossbreed, Brendol, lost a leg to osteosarcoma. On the rescue forum she found another dog, Addy, whose leg had been amputated and who needed rehoming. “I already had one three-legged dog, but I just kind of jumped in.”

Day two, and, after a drunken evening playing Cards Against Humanity at a house on the Mattaponi river, people’s real names are beginning to usurp their usernames in my mind. For Sally Holladay (Benny55), Tripawds “gives us the format to be who we are – you don’t see faces or ages or anything like that. You just see heart.” We are sitting at a picnic table, and every so often, Merry Myrtle, her 125lb bullmastiff, hauls herself up in between us. “I’m not into all that training,” says Sally, smiling a little sheepishly. She speaks in a fabulous southern drawl. “Mostly I just love ’em.”

Sally, who is 70, and describes herself as “the world’s oldest waitress”, found the community four years ago after her previous bullmastiff, Happy Hannah, lost a leg to osteosarcoma. “I was so alone, so isolated. Nobody understood.” Her partner had died more than a decade before from an aggressive cancer. “I kept saying to him, Billy, what should I do, ’cause Billy would have known what to do.” It was six days after Hannah’s amputation that Sally first posted on Tripawds. “They threw me a lifeline,” she tells me, “and I held on.” From her home in Powhatan county, Virginia, surrounded by rescued dogs, Sally spends hours every day responding to posts on her crack-screened tablet, supporting, grieving each loss, celebrating every triumph. It was she, among others, who persuaded me that it was at least worth giving Meg a chance of a decent life on three legs.

Facebook Twitter Pinterest Karma Bevelhimer with Adelaide, Maggie May and Aissa. Photograph: Jared Soares/The Guardian

Many visitors to the site first post in a panic after learning their dog needs to lose a leg, and later drift away; but there is a core group who stuck around, offering support and advice. Michelle Doner’s rottweiler, Sassy Sugarbear, died almost four years ago. She posts daily and also volunteers, answering calls on the helpline. A 40-something insurance analyst from Council Bluffs, Iowa, I find her sitting beside a stall selling collars to raise funds for greyhound cancer, and she seems on the verge of tears. She has travelled to meet her “family”, and it is, she explains, “a lovely and emotional thing”.

Nearby stands the Tripawd Angels table, bearing framed pictures and mementoes of tripawds who have died. Some are very recent losses: Isa, with her gentle, pleased-looking face; proud, handsome Pofi. These are dogs I knew, dogs whose journey I followed, whose loss I mourned. Others have been gone for longer: Hannah, Max, Sassy Sugarbear, Brendol, Shelby Lynne, and Jerry, who started it all. A tribute leash carries dozens of colourful ribbons, some simply bearing a cat or dog’s name, others lavishly bejewelled, or decorated with squirrels and balls, a tag, an embroidered rabbit.

Facebook Twitter Pinterest The Angels table, with tributes

to former pets. Photograph: Jared Soares/The Guardian

“These people know more about me than probably some of my closest friends,” says Alison Raitt (Mom2Shelby), who is tying on Shelby Lynne’s ribbon. Rescued from a New Orleans shelter, when Alison was 28, Shelby Lynne lived with her throughout her 30s. Through a series of break-ups, Shelby was Alison’s constant companion, and when, aged 12, she was diagnosed with the deadly hemangiosarcoma, Alison’s friends predicted there would be “the shit storm of the century”. Alison says the Tripawds experience has changed her profoundly. “You’re behind a screen, so you can be as vulnerable as you want to be. I don’t think I’ll ever not be part of Tripawds. It’s a way of life now.”

There’s a lot of hugging as the “pawty” draws to a close. “It’s like a dog’s life: too short,” says Sally and there are tears in our eyes as we embrace. But it’s time to head home to the raggedy mutt I brought home that day from the churchyard. Sixteen months after her amputation, Meg is loving life and demonstrating on a regular basis that a dog on three legs can cause as much mayhem as any dog on four. The future is uncertain, but I am determined to Be More Dog. If only Meg could be a little less so.