Knee reconstructions for young Australians are on the rise, posing an expensive and painful public health problem in the future, a new study has found.

The number of young Australians undergoing knee reconstruction surgery has risen more than 70 per cent in the last 15 years, according to the study published today in the Medical Journal of Australia, with the greatest increase among children under 14.

[Warning: This story contains an image of surgery that may disturb some readers.]

Knee reconstructions are most often required when the anterior cruciate ligament (ACL) — important for maintaining stability in the knee — is damaged.

Rupture of the ACL typically happens when someone changes direction at speed while playing a multi-directional sport, such as AFL, rugby or netball.

And while Australia has the highest reported rates of ACL injury and reconstruction in the world, lead researcher Christopher Vertullo, director of Knee Research Australia, said ACL injury is largely preventable.

A decade of pain

An ACL rupture at a music festival when she was 21 has dogged Kirraly Osborne for a decade.

The night had barely begun when Ms Osborne made a sudden turn on her right leg, where she had some niggly pain caused by netball and dancing.

She then found herself on the ground — unable to stand up.

Kirraly Osborne ruptured her ACL at a music festival when she was 21. ( Supplied: Kirraly Osborne )

"I just remember turning, super sharp pain, falling over," she said.

"I remember thinking 'that's weird' … just trying to stand up again and the sheer pain — I just fell straight back down again."

What followed was 10 years of surgeries, physiotherapy, cortisone injections — and more pain.

"I've felt some sort of pain in my knee … probably every day at some stage for the whole of the 10 years [since]," Ms Osborne said.

The injury affected both her ACL and her figure-eight-shaped medial ligament, leading to five surgeries on the joint.

These days, she has made her peace with the fact her knee is never going to be the same again.

"That's just life. I know what my body can and can't do and I just do what I can," she said.

Football, netball connected to many injuries

Nearly 200,000 ACL reconstructions were performed in Australia between 2000 and 2015.

What is an ACL? The anterior cruciate ligament is an important ligament that helps stabilise your knee

The anterior cruciate ligament is an important ligament that helps stabilise your knee Torn ACLs can cause the knee to collapse when trying to twist or turn

Torn ACLs can cause the knee to collapse when trying to twist or turn Repairing torn ACLs typically requires replacement tissue from somewhere else in the body

Repairing torn ACLs typically requires replacement tissue from somewhere else in the body Australian rules football, rugby, soccer and netball are all high-risk sports Source: Better Health Channel

The annual incidence increased by 43 per cent, and by 74 per cent among those under 25 years of age, Associate Professor Vertullo said.

"The rise of ACL injury in young people has been attributed to earlier specialisation by younger athletes, longer sporting seasons, more intense training, higher level of competition, and a lack of free play," he said.

According to the study's findings, about 72 per cent of ACL reconstructions in Australia are sport-related — and the sports most frequently involved are Australian rules football, rugby union, rugby league, netball, basketball, soccer, and skiing.

In Australia, men aged 20 to 24 years and women aged 15 to 19 years are at greatest risk of an ACL injury.

And while the research shows girls and women are two to 10 per times more likely to rupture their ACL when participating in high-risk sports, the researchers found men in older age groups had a higher incidence of ACL reconstruction surgery.

"It is conceivable that the higher incidence in males reflects greater participation in sports such as Australian rules football, in which pivoting, jumping and rapid deceleration increase the risk of ACL injury," the study's authors wrote.

Children's sport getting more professional

The study found the greatest increase in ACL surgery cases between 2000 and 2015 was in children aged between five and 14 years of age — surgery in boys was up by 7.7 per cent, and girls by 8.8 per cent.

According to the researchers, the "worrying" increase in ACL injury and reconstruction among young people was at least in part because of the increasing pressure in kids' sport.

"The increased incidence in children is of particular concern, as ACL injury in this age group was previously rare," the authors wrote.

"The burden of future degenerative disease falls most heavily on our youngest patients."

Other factors contributing to the rise in knee reconstructions include increasing medical and public awareness of the procedure, diagnostic improvements, the availability of magnetic resonance imaging (MRI), and increased access to orthopaedic surgeons.

Costly surgery and health outcomes

From 2014 to 2015, the total direct hospital costs of ACL reconstruction surgery in Australia were estimated to be $142 million.

Nearly 200,000 ACL reconstructions were performed in Australia between 2000 and 2015, many on people under 14. ( Getty: John P Kelly )

The average cost of an ACL reconstruction, including hospital fees, is $8,364.

On the top the financial expense, rehabilitation and recovery times can be long, and the injury puts people at greatly increased risk of osteoarthritis in later life.

"The short-term consequences of ACL rupture include the inability to participate in sport, reconstructive surgery, and prolonged rehabilitation," Associate Professor Vertullo said.

"In the long term … almost all individuals who tear an ACL are at increased risk of osteoarthritis and disability."

And when people injure their meniscus at the same time, like Ms Osborne did, this risk is substantially increased, Associate Professor Vertullo said.

Prevention is key

ACL injuries may be increasingly common, but the research shows most are preventable.

Regular neuromuscular agility programs, which help develop healthy movement patterns and strengthen muscles around commonly injured joints, can stave off 50 to 80 per cent of ACL injuries, Associate Professor Vertullo said.

"Prevention is much more cost-effective than either ACL reconstruction or rehabilitation," the study's authors wrote.

"Establishing a national ACL injury prevention program has been reported as a cost-effective strategy for improving sporting health outcomes for young Australians.

"The increasing incidence of ACL injury in Australia is an emerging public health problem, with potentially detrimental long-term health outcomes, especially for young people."