text: They say that the new material is more robust and hardwearing than previous efforts to create artificial cartilage.
  A traditional ink-jet printer combined with a specialised spinning-machine is used to make it.
  It could lead to bespoke cartilage created for individual patients. But one expert warned it was too early to be confident it would ever be used.
  The study was published in the Institute of Physics' journal Biofabrication.
  It marks the latest effort to use 3D printers in medicine following the use of a machine to make a replacement lower jaw and efforts to create 3D-printed scaffolds to support the growth of bone cells.
  Scientists said they were able to build cartilage made from a chemical compound known as a polymer coated with cartilage cells from a rabbit's ear.
  They combined the ink-jet printer with a machine that uses an electric current to spin very fine fibres from the polymer solution.
  It allowed the construction to be easily controlled, meaning scientists could make the artificial cartilage porous. This is key to encouraging real cartilage cells to integrate into the surrounding tissue.
  So far the printed cartilage has been tested on mice and, after eight weeks, appeared to have developed the properties of real cartilage, suggesting it has potential for insertion into human patients.
  The scientists said that in the future it could allow medics to create cartilage specific to each patient's needs.
  They suggest an MRI scan could create a blueprint of a body part, such as a knee, and matching cartilage could be made using the 3D printer.
  "This is a proof-of-concept study and illustrates that a combinations of materials and fabrication methods generates durable implantable constructs," said James Yoo, a professor at the Wake Forest Institute for Regenerative Medicine, and one of the paper's authors.
  At present one of the best options available to doctors treating cartilage damage is a technique called microfracture surgery.
  It involves drilling small holes into the bone in the cartilage's gap to encourage bleeding. Scar tissue then forms over the gap, acting as a replacement for the missing cartilage.
  But it is not generally suitable for older or more obese patients, and it does not work if the lesion is too large.
  Dr Richard Weiler - a consultant in sport and exercise medicine at University College London Hospitals - told the BBC the new innovation could potentially offer respite to a wider range of the patients he treated. But he had doubts about whether it would ever be used.
  "Certainly with sport there are injuries that cause damage to cartilage - we have seen this with some famous footballers, cyclists and other athletes who have had traumatic injuries where the cartilage has been damaged and then drops off and doesn't grow back very well in the affected area," he said.
  "However, there have been lots of previous cartilage replacement technologies that were shown to have had an effect in animals but have proved not to be as good as hoped when used long-term by humans.
  "This technology sounds an interesting development, we would just want to make sure it's safe."
target: Researchers have developed a way to "print" cartilage that could help treat joint diseases and sporting injuries.