"He was such a cranky child," she said. "I used to say to [my husband] Nick when he was a baby 'There's got to be something that's not right here'."

"Surely babies can't be born this miserable?"

Lennon's instinct was correct.

When Matthew began walking at 15 months, he did so with a limp.

Lennon, from Glenbrook, recalled telling her husband: "Let's not be too paranoid. If we still think it's there in a couple of weeks, we'll go and see someone about it."

Matthew was diagnosed with hip dysplasia (also known as developmental dysplasia of the hip) - a condition where the ball and socket of the hip joint fail to form properly.

The diagnosis was a surprise to Lennon, who said: "He had check-ups with the GP and community nurse and nothing had been picked up by them."

Nicole Williams, a paediatric orthopaedic surgeon at the Women's and Children's Hospital in Adelaide, said there were a number of risk factors associated with hip dysplasia.

"These include having a family history, female babies, first born, breech presentation, large babies," she said. "Babies who are wrapped up or swaddled with their legs held tightly together and out straight also have a higher risk of [hip dysplasia] and this should be avoided."

In contrast, Dr Williams said rates of the condition were "very low" in cultures where babies are carried with their legs wrapped around their mother and flexed into an "M" position.

The risk associated with swaddling was also highlighted in The Medical Journal of Australia in 2016.

"There is growing concern among the orthopaedic fraternity in North America, the UK and Australia that a resurgence in the popularity of swaddling, including the increased use of "swaddling cocoons" (which force the lower limbs into extension), places children at risk of late diagnosed [hip dysplasia]."

The authors said there had been an increase in the late diagnosis of infants with hip dysplasia in several Australian states, which can lead to a range of poor outcomes: "This includes increased likelihood of surgery, more invasive surgical procedures, longer hospital stays, and early osteoarthritis of the hip, as well as increased health care costs."

Dr Williams said early detection was important as babies diagnosed before the age of three months were less likely to require complex surgery.

"Unfortunately in Australia, rates of [hip dysplasia] diagnosed after three months of age have increased in the last 15 years," she said.

The rate of infants treated for hip dysplasia in Western Australia, which keeps detailed records of birth defects, almost tripled between 2010 and 2014 to one in 50 - similar increases have been reported in other states.

Matthew underwent surgery five weeks ago to correct the dislocation by taking a bone graft from his pelvis and rebuilding the hip socket on his left side.

He will be in a spica cast for at least six weeks before wearing a brace.

Lennon said the armpit-to-ankle cast is designed to prevent her two-year-old son from moving his hips or putting weight on his legs.

"He gets frustrated," she said. "He can drag himself around a bit, but if he is going any distance he need someone to pick him up and move him."

Sarah Twomey, the founder of Healthy Hips Australia, which aims to increase awareness of the condition, has two children who suffer hip dysplasia, including daughter Eve who spent 10 months in a full-body harness followed by a hip brace.

She said treatment can be a source of frustration when trying to learn developmental milestones and trying to settle to sleep.

"The professional view is that hip dysplasia is not believed to cause pain in babies, and often won't prevent them from learning to walk," she said. "Left untreated however, pain is the most common symptom from adolescence onwards."