Kenzie Davie, 15 months, broke her femur playing at a trampoline park. Photo / Supplied

A Christchurch mother is warning parents to be cautious after her 1-year-old broke her femur on a visit to a trampoline park.

Charlotte Davie took her two children to the trampoline park for an under-5s session on Friday last week.

She was talking to her 3-year-old son when she heard Kenzie, who is 15 months old, crying.

The toddler was sitting on the trampoline "grizzling" but Davie did not think much of it.

"It was quite a quiet grizzle ... I just gave her a cuddle," she said.

But after about 20 minutes, Kenzie was still upset, so Davie took her to the 24-hour centre for a check-up.

Kenzie was x-rayed, and after about two shots were taken Davie was told there was a "clear fracture" in the child's femur and she needed to be taken to hospital.

"I felt so guilty as a mother, you always do," she said.

"We all know that trampolines have their dangerous moments."

It was unclear how the injury happened.

They went by ambulance to hospital, where Kenzie was placed into traction, with her legs hoisted up at a 90-degree angle to keep the bones from fusing incorrectly while they waited to put her in a cast.

Kenzie was kept in traction for 48 hours until a paediatric anaesthetist and special casting team could be assembled to put her into a cast under general anaesthetic.

"At the 50-hour mark, I could finally pick her up and cuddle her."

It was "very gut-wrenching knowing you can't pick up your baby when they're crying for you".

Doctors told Davie her daughter will need to be in the cast - which covers both legs - for up to six weeks.

Davie wanted to warn other parents of the dangers of trampolines for small children, and encourage them to be "cautious".

"I didn't anticipate it would happen to me and it would happen to my daughter."

Paediatric orthopaedic surgeon Dawson Muir said the main ways small children broke their bones on trampolines was from being double-bounced or fallen on by a larger child.

Most of these injuries tended to be further along the limb but it was also possible to suffer femur fractures, he said.

While toddlers can have lower bone density during a growth spurt they are not more likely than others to suffer a fracture, and most trampoline injuries happen to children in higher age groups.

ACC receives about 12,000 new claims each year in relation to trampoline injuries, with the majority being soft tissue injuries followed by fractures and dislocations. They also received claims for lacerations, dental injuries and concussions.

The most common area to injure was the ankle, with back and spine, knee, face, neck, back of head and arms all being reported a similar number of times.

Last year ACC received 2365 new trampoline-related claims for children under 4.

The most at-risk age group was 5-9, with 4170 claims, then 10-14 with 2793.

ACC's active costs for trampoline claims last year reached more than $10 million.