As Megan's legs stiffen and bend, her bones begin to deform and walking becomes impossible. She used to be able to walk with poles but as she hit her teens and began to grow, the tightness has become worse and worse and now she must use a wheelchair.
Megan's family have been approved for selective dorsal rhizotomy surgery in St Louis, Missouri, in which surgeons will find the nerves sending the defective messages to her muscles and turn them off, followed by another operation to stretch her tendons.
That in turn will be followed by four weeks of intensive rehabilitation in the US learning to walk, and two years of rehabilitation physiotherapy in New Zealand.
They hope the operation will successfully remove the spasticity from her muscles and allow her to walk without needing a wheelchair or walking frame.
Other children in New Zealand have gone to the US for the operation and their stories have given the family hope that Megan too can one day walk unaided.
It is a daunting prospect, with the added worry of trying to raise the money needed.
However they are doing everything they can to make sure they reach the total, no matter how big or little. Every evening Melissa and whichever children are free go house to house in Hamilton selling chocolate bars to raise money.
Their church is holding a half marathon in December and hoping for a good turnout. Megan's grandparents and parents have been selling raffle tickets for $1.
Megan's grandparents live in Taupo and recently Megan and her parents were at Pak 'N Save in Taupo spreading the word. The family is using every network in a desperate attempt to find the money by March, when the treatment will have to be paid for, and while dad Craig has a good job, it's a struggle.
But every donation helps the family inch closer to their goal of helping Megan to walk.
It is not a cure, but it the only option they have.
"We sat there," says Melissa of the moment the family got the news Megan had been accepted for the surgery, "and we said 'what are we going to do?' And we said 'well, this is the best surgery and if the only thing that's stopping us is the money then that's not good enough', so we decided to do this."
In the space of a year Megan's mobility has deteriorated so much that she has gone from using walking poles to a walking frame, and now a wheelchair. She is a normal teenager and gets upset when she can't join in the activities that her friends enjoy. Her family is trying to keep Megan as mobile as they can to get her to St Louis.
Megan has a givealittle page, but people can also deposit money directly into an account, ensuring she gets 100 per cent of the donation. Details are at Facebook/Megans SDR Dream.