The 3D scaffold is made from a woven material that can bear up to 10 times a patient's weight, letting them to exercise and otherwise live normally. It can even solve the original cause of the program, which is usually osteoarthritis. Using gene therapy, they genetically programmed the joint to release anti-inflammatory molecules on demand to keep the arthritis at bay. "Our hope is to prevent, or at least delay, a standard metal and plastic prosthetic joint replacement," says Washington University Professor Farshid Guilak.

Lest you protest that this potential treatment is reserved for your elders, think again. "We envision in the future that this population of younger patients [aged 40-55] may be ideal candidates for this type of biological joint replacement," says researcher Bradley Estes. That's because doctors are often reluctant to perform joint-replacement surgery on patients younger than 50, because they'll need a second operation when they're older and more at risk for infection and other issues.