INDIANAPOLIS -- A study is checking whether an injection of adult stem cells can re-grow the spongy tissue between people's shinbones and their thighbones. The injection would be for people who have surgery to remove torn parts of a meniscus. The surgery can lead to trouble in the future if arthritis sets in where the tissue is missing. Doctors hope that a stem-cell injection after such a surgery can re-grow meniscal tissue so future problems can be avoided. In animal studies, the shot led to tissue regeneration in 11 weeks. If it works in humans, it could change the way...