Researchers at a U.S. university say they've developed a better recipe for creating a synthetic replacement cartilage for human joints. In a study reported in the journal Advanced Functional Materials, scientists at Duke University describe the production of artificial replacement tissue that mimics both the strength and suppleness of natural cartilage. Cartilage, the tissue on the ends of bones where they meet at joints in the body – including in the knees, shoulders and hips -- can erode and degrade over time or be damaged by injury, disease or overuse, causing pain and lack of mobility. The Duke researchers say they've used tiny interwoven fibers to create a three-dimensional fabric "scaffold" into which a strong, pliable hydrogel is integrated and injected with stem cells, forming a framework for growing cartilage. A suitable hydrogel has been the goal of the research; materials supple enough to simulate native cartilage have been too squishy and fragile to grow in a joint and withstand loading, while stronger substances haven't been smooth and flexible enough, the scientists said. The research team has developed a water-based polymer gel that meets the criteria. "It's extremely tough, flexible and formable, yet highly lubricating," said Xuanhe Zhao, a Duke professor of mechanical engineering and materials science. "It has all the mechanical properties of native cartilage and can withstand wear and tear without fracturing. "From a mechanical standpoint, this technology remedies the issues that other types of synthetic cartilage have had," Zhao said. "It's a very promising candidate for artificial cartilage in the future."