Knee osteoarthritis (KOA) affects more than 1 in 10 people older than 40, impairing patients' mobility and quality of life. With limited treatment options, stem cell injections have been promoted as a treatment, but clinical trial evidence of efficacy is often lacking, despite claims from clinics selling untested options. Even where well-designed clinical trials have been performed, there is no clear consensus about the benefits of stem cell injections for KOA, likely because of the many variabl