Mrs Smith, 56, of Warkworth, doesn't know where to turn for help. She sometimes sobs in pain and frustration as she tells how for five years since the amputation of her lower left leg she has struggled to regain a normal life.
The Artificial Limb Service, which runs limb construction and fitting centres in five cities, couldn't give clear answers on why it has been unable to solve Mrs Smith's dilemma.
"Currently I am unsure as to why the various limbs made for Diane Smith have not been successful, given the high level of involvement Diane has had with each of the six different prosthetists she has now worked with," said chief executive Mervyn Monk.
He contrasted her case with the "remarkably high level of amputee satisfaction with the limbs provided" - typically 87 or 88 per cent - found in surveys done for the service.
In 2003, Mrs Smith fell and received multiple fractures in her ankle and a dislocated knee. The screw and plate used to repair her ankle were too long and caused serious blood-flow problems. The lower leg had to be amputated to save her life.
She said she got the impression "these people at the limb centre had the best equipment and were really on to it".
But after five years, she has lost confidence in the limb centre.
Mrs Smith said she suffered six haematomas - a swelling of clotted blood - on her stump last year and some became infected. They put her at risk of higher amputation.
At present she is experiencing severe pain and can walk with a prosthetic on for no more than 10 minutes before having to remove it and revert to crutches.
She blamed the limb centre's "old-school" methods, saying it preferred a tape measure to computer-assisted design (CAD) techniques and was unwilling to use costly, although lighter, carbon fibre instead of fibreglass on prosthetics for older women.
But Mr Monk said staff were very experienced and kept abreast of global developments in prosthetics.
"All limb centres use Tracer CAD as appropriate for the amputee and/or level of amputation ... it achieves the best results for amputees who have an above-knee limb loss."
"Tracer CAD is not always the best solution ... OSSUR, the company that designs and supplies the socket interface used for Mrs Smith is quite clear that a hand-casting and measuring approach is required."
He denied carbon fibre was reserved for clients younger than 50, saying the materials used depended on how active the person was.
"Carbon fibre is not always used though, because it can make a socket very rigid - non-flexible - which in some socket designs is not desirable."
Mrs Smith has complained to the Health and Disability Commissioner's Office, which has appointed an advocate who will attend a meeting at the limb centre with her this month.
The Accident Compensation Corporation has referred Mrs Smith to a private prosthetist in Wellington, who has made an initial assessment. Mrs Smith says this is looking like a promising alternative but she is undecided about agreeing to having her limb made in Wellington.
Bad prosthetic blamed for loss of second leg
Double-amputee Sharon Goodwin blames the loss of what was her remaining good leg on a poorly-fitting artificial limb.
Sitting in a wheelchair at her home in Swanson, West Auckland, Mrs Goodwin, 60, says her first amputation, of her right leg below the knee in 2004, was the result of Sjogren syndrome, an auto-immune disorder that causes inflammation of blood vessels which leads to ulcers.
In 2008, she had a fall which damaged the stump, resulting in amputation above the knee.
Below-knee prosthetics and later above-knee models made for her by the Auckland Limb Centre - around 10 limbs in all - never worked properly, she said.
"I had a fall last year, about February at Pak 'n Save in Henderson because my leg was not fitting properly.
"I broke my arm and the fall knocked my left leg and that caused an ulcer on the ankle that didn't heal. That came off below the knee last September."
Mrs Goodwin says she longs for an artificial leg like the one used by medal-winning Paralympics swimmer and amputee Sophie Pascoe.
"I am entitled to have as good a leg as Sophie Pascoe and all the other people that run and swim and ride."
Like Diane Smith, Mrs Goodwin lost confidence in the limb centre's ability to make her a good leg. That has been rectified in part by the appointment of a new prosthetist who has spent much longer working with her.
Artificial Limb Service chief executive Mervyn Monk says the prosthetic Mrs Goodwin was using when she fell at the supermarket had not been reported as defective.
"We agree that it has been more difficult than usual to assist Sharon to provide a prosthetic leg that achieves the ideal fit for her, but every endeavour has been made to assist her," he said.
