As  physician groups’ market share increases, they gain bargaining power with payers, which may in turn drive up medical costs, says a study in Health Affairs.

Becker’s Hospital Review reports on the study that “Researchers from the Stanford University School of Medicine found orthopedic surgeons in concentrated markets charged 7 percent more for knee replacements than surgeons in less concentrated markets between 2001 and 2010, even as the average cost of knee replacements nationwide dropped $261. In the most concentrated markets, fees for knee replacements increased $168 on average compared to the least concentrated physician markets.”