Replacement hips and reconstructed knee joints are becoming more commonplace, but what happens to them after you die?

In 2013-14, a total of 72,551 hip and knee replacement operations were performed on patients with osteoarthritis according to the Australian Institute of Health and Welfare, and there are currently 1.8 million Australians living with the degenerative joint disease.

More than 72,500 joint replacement operations were undertaken in Australia in 2013-14. ( ABC News )

And the growing medical trend to replace joints has provided an interesting challenge for morticians after someone has been cremated.

"The skeletal remains which are left at the end of a cremation are raked out manually into a tray where they are left for a couple of hours to cool," Robert Pitt, chief executive of the Adelaide Cemeteries Authority, told 891 ABC Adelaide's Afternoons program.

A magnet is then run over the ashes to lift out any metal, while large replacement joints have to be removed manually.

"Titanium doesn't melt down so most of the large hip, knee and shoulder replacements are physically removed," Mr Pitt said.

Hips, shoulders and knees recycled

Mr Pitt said twice a year the local crematoriums shipped the joints to Melbourne.

The joints are then combined with other collections from around the country and shipped to the Netherlands.

"There is a company called OrthoMetals who have a purpose-built facility for recycling and separating all of the metals," he said.

"In one year we do just over five tonnes of recycled metals."

The service is provided free of charge to crematoriums and every six months a percentage of revenue raised from the recycled metals is given back.

The Adelaide Cemetery Association receives about $12,000 a year from the recycling program.

"We have a special fund that our board looks after," Mr Pitt said.

"The board uses the funds from the recycled metal to support an appropriate cause."

Things that make you go boom

Although metal-based medical devices are relatively harmless to pass through the cremation process, others can be quite dangerous and need to be declared.

Battery-powered medical aids such as pacemakers, for example, explode inside cremators.

"The funeral director removes that prior to the deceased person being delivered to the crematorium," Mr Pitt said.

"The exploding battery can do quite a lot of damage inside a cremator and makes a very loud noise if it is not removed."