Warning: Some readers may find the photos in this article graphic.
Elsie Moravek, four, was born with proximal femoral focal deficiency (PFFD), meaning her left leg was considerably shorter than her right.
Parents Jackie Moravek, 28, and Matt Moravek, 31, were told they had three options – to amputate Elsie's leg, fit a prosthesis or lengthen her limb by 11cm.
They opted to lengthen her leg, which involved having pins "drilled into her bones".
"We asked ourselves if we were being cruel to put our daughter through this and whether it was worth it," Mrs Moravek from Kalamazoo in Michigan, America, said.
"But we knew it was the right decision. We wanted Elsie to have the best life possible."
Before the lengthening began, Elsie had to have a six-hour operation reconstructing her knee, ankle and hip.
During surgery, Elsie's femur (thighbone) and tibia (shin bone) were fitted with an external device, with ten pins piercing through her skin, muscle and bone.
She was fitted with a prosthetic foot, which bridged the gap between her real foot and the floor.
Three times a day, Elsie's mum had to manually turn screws to pull apart her daughter's femur and tibia a millimetre a day, preventing the break from healing each time.
New bone, muscle and skin grew in its place as the leg gradually lengthened by 11cm over four months.
Elsie was on constant pain medication throughout her treatment.
"I felt very helpless. I was very pleased with her progress but it was hard to see her in pain and crying," Mrs Moravek said.
"I would have to put my mum hat on and push through it because I knew what the end result would be.
"Cleaning the open wounds where the ten pins had been drilled into her bone was the worst.
"It was agony for her.
"I felt upset watching her go through it, but we had a goal in mind."
Now, four-year-old Elsie's legs are even – but, as her left limb still has a growth deficiency, the family have been told her legs will grow out of sync again.
She will require another procedure to lengthen her left leg by a further ten centimetres once she reaches her full height.
Mrs Moravek added: "We wanted to give Elsie the best life possible and we thought the best option was to lengthen her leg.
"That means she won't need a prosthetic or to get her leg amputated so she can do everything other girls her age are capable of.
"We made a lot of sacrifices for this, but every single one of them was worth it."