An onlooker, Konstantinos Metaxoulis, climbed up the colourful maze of tunnels to free the five-year-old, and handed him safely back to his parents at the restaurant in Sydney's north-west.

But after helping the boy, Mr Metaxoulis fell two metres to the ground, and badly hurt his left wrist, aggravating an earlier injury, and leaving him feeling like "someone put a knife [in] and slowly turned it".

Mr Metaxoulis, a Sydney chef, sued McDonald's for negligence, and last year a NSW District Court judge found he had not proved his case.

But Mr Metaxoulis has successfully appealed against the decision.

The NSW Court of Appeal awarded him $179,000 in damages on Monday, finding that the risks at the Castle Hill playground were "readily foreseeable".

The court heard Mr Metaxoulis had a motorcycle accident in Greece in 2004, and fractured a bone at the base of his left wrist.

Soon after the fall from the equipment, on July 31, 2010, he went to a hand surgeon, who said surgery would help the pain but would not return the wrist to normal.

In 2012, an orthopaedic surgeon said that Mr Metaxoulis's job as a chef would be affected as he could only do light, non-repetitive work, and lift nothing heavier than five kilograms.

Mr Metaxoulis told the District Court he took Panadeine Forte every day and, while working in kitchens, he suffered pain that felt like "someone pulling my wrist apart".

His wife told the court his mental health had also suffered, and he could not do work around the house.

The court heard that the boy got trapped between the outside of the tunnels and a barrier at McDonald's Playland, on a rear part of the equipment that could be accessed for cleaning through a gate, but was fenced off to stop children from climbing on it.

There was evidence that the gate did not have spring-loaded hinges, meaning that it would have stayed open if someone had unlatched it.

It also did not have a sign restricting access, or a key lock, like those used on some swimming pool gates.

"Once open it was foreseeable, indeed to be expected, that young children would use it to gain access to the back area of the colourful equipment," Justice John Basten wrote in the Appeals Court judgment, agreed to by Justice Ruth McColl and Justice Robert Macfarlan.

"Once in that area, it was also to be expected that they would, if they could, climb on to the colourful equipment. The risk of getting stuck, or slipping off, was also readily foreseeable."

Mr Metaxoulis was awarded damages for past and future economic loss, as well as for non-economic loss.

McDonald's was ordered to pay his costs for both legal proceedings.