An article from the Wellcome Trust: "Researchers have been engineering cartilage in the laboratory for 15 years or more, but as yet the tissues they have created don't function properly in human joints. [Researchers] are taking a new approach to try to bridge the gap between laboratory-created cartilage and the tissue our bodies make. ... Biological texts show that these lab-grown tissues have the appearance, texture, and protein and mineral components of bone and cartilage. But once they are tested in an animal, these tissues simply don't behave quite like the natural tissues they are supposed to replicate. ... Joints are remarkable feats of engineering, but efforts to grow them in the lab have focused mostly on their biology. ... Biologists attempting to create cartilage and bone over the past 15 years have typically tested the mechanical properties of their laboratory-grown tissue - for example, whether it is rubbery and resilient enough when pressure is applied. ... Just because biological tests indicate a tissue looks like bone and feels like bone, doesn't actually mean it is bone ... This is where an engineering perspective becomes important. To look at how close a match these laboratory-generated tissues really are to native bone and cartilage, [researchers] supplemented the biological analyses with engineering tests, such as bio-Raman microspectroscopy. ... You shine a laser on the material, and the way the light scatters gives you an idea of the bonds between its components. Different mineral types form different bonds, so you get a much more precise picture of what is actually present. ... If a lab-grown tissue seems from some tests to be the real thing but isn't really, then it won't behave like it once it has been implanted in a human body. ... [The researchers aim] to use an engineering approach to create a whole osteochondral interface in which bone and cartilage transition seamlessly into each other like they do in the body. ... That's the only way it will effectively transmit loads to the underlying bone. And because bone will heal, it will heal the construct into the joint."