"If you really want to try and calm a knee down and you don't want to put in something detrimental like cortisone, you can put something healthy in there like stem cells," Yoon said. "With these stem cell injections, there are a lot of other things that are in that injection – growth factors, anti-inflammatories, material that can help with tissue healing. It's becoming more and more popular. As every year goes on, especially in professional sports, physicians and providers are realizing there's a lot of upside with these injections and there's very little downside."