A woman has narrowly avoided jail for starving a Staffordshire bull terrier to the point it was just "skin and bone" in one of the worst cases of animal neglect that the Adelaide Magistrates Court has ever seen.

Key points: RSPCA officers first went to Nancy Jane Thomson's Sefton Park home in August 2016

RSPCA officers first went to Nancy Jane Thomson's Sefton Park home in August 2016 The court heard Charlie was a "walking skeleton" and in a "horrendous condition"

The court heard Charlie was a "walking skeleton" and in a "horrendous condition" Thomson received a three-month suspended sentence

Nancy Jane Thomson, 57, pleaded guilty to two counts of ill-treating an animal moments before her trial was due to start on Wednesday.

The court heard a complaint was referred to the RSPCA about the terrier, named Charlie, and his poor condition in August 2016.

However, when an inspector attended Thomson's Sefton Park home, she showed them her two other dogs — one of which was slightly underweight.

The inspector gave her some feeding advice and left.

It was not until a second complaint was made about two weeks later that an inspector reattended and found Charlie, who appeared emaciated with his ribs, hips and spine clearly visible.

A court heard RSPCA officers were first called to Nancy Jane Thomson's Sefton Park home in August, 2016. ( Supplied: RSPCA )

The court also heard that Charlie's claws were so long that they had curled all the way around and were embedded into his feet pads, causing him significant pain and making it difficult for him to stand.

Magistrate Paul Foley ordered Thomson to serve a three-month suspended sentence and pay $6,425.78 in vet and boarding costs sought by the RSPCA.

"I'm not sure having sat for a number of years now and dealt with a number of these cases that I've seen an animal in poorer condition than this one," he said.

"I regard this as one of the most serious examples of neglect that I have seen.

"He was literally skin and bone, there is no flesh to be seen on the dog whatsoever."

Nancy Jane Thomson pleaded guilty to two counts of ill-treating an animal. ( ABC News: Rebecca Opie )

Outside court, RSPCA Inspector Cheryl Doudle said when Charlie was seized he looked like a "walking skeleton".

"The dog was in a horrendous condition, it was the skinniest dog I have ever seen, I was surprised it was still alive," she said.

"It was just like a walking skeleton, he had no hair, you could see every single bone in his body.

"I don't know how you can go to sleep at night and see a dog in such poor condition just wasting away."

Through her counsel, Thomson argued that Charlie belonged to her mother-in-law and that she only realised his poor condition when her mother-in-law died about three weeks before the RSPCA attended.

Magistrate Foley rejected Thomson's claims that she rarely saw Charlie because she did not want to interfere with her mother-in-law, who Thomson described as a "strict woman".

"You were living in the house as a carer for your mother-in-law, the dog, I accept was spending most of its time with her but it defies reasonableness as to conclude that you weren't aware of the condition the dog was in," he said.

"I accept that she might well have been the principal carer for the dog but she was someone who needed care from you, herself."

Charlie now lives with a foster family. ( Supplied: RSPCA )

In just a few weeks of proper care and feeding at the RSPCA, Charlie gained 37 per cent of his body weight.

The dog returned to full health and now lives with a foster family.

The court imposed a supervision order to ensure Thomson's two other dogs are adequately cared for and banned her from owning any more animals.

She shook her head in the dock while the details of her offending were discussed in court.