A major trend in contractual payment arrangements between medical providers and payers, intended to lower costs while improving the quality of care, triggers cost-shifting from group health plans to workers’ compensation, according to a new study reviewed by the CFO website. The shift hinders some employers from reaping the hoped-for cost benefits, study results suggest.

More medical providers are agreeing to full or partial capitation arrangements, under which they’re paid a set amount for each enrolled plan member assigned to them per period of time. It’s a counter to the fee-for-service model, under which providers have a financial motivation for ordering care that a patient may not actually need. Most recently, Blue Cross Blue Shield of Massachusetts, the state’s largest health insurer, announced new deals with three large health systems that “set budgets to care for patients and reward providers for keeping patients healthy and away from expensive hospital stays and procedures,” the Boston Globe reported.

Meanwhile, the prevalence of capitation arrangements is on the rise. A late-2014 study of reimbursements for care provided to 101 million people, conducted by Catalyst for Payment Reform, an employer-funded health policy group, found that 15% of what health insurers spend on medical bills is paid under capitation.

In some states, it’s a much bigger slice of the pie. For example, for Blue Cross Blue Shield of Massachusetts, 40% of its 2.1 million individual members will be, as of Jan. 1, covered under health plans that shift financial risk to medical providers.

That all sounds good – but there’s a little-discussed wrinkle. That is, for some common ailments, like soft-tissue back, knee, or shoulder pain, it’s often not clear whether the injury was work-related or non-occupational. Doctors are given a degree of discretion under workers’ compensation law to make that determination, which creates a conflict of interest, because they usually end up benefiting financially by classifying the injury as work-related.

A recent WCRI study found that soft-tissue injuries suffered by patients covered under capitated group health plans were 11% more likely to be classified as work-related. And that proportion rose to 31% in states where at least 22% of workers were covered by capitated plans. According to WCRI, if just 3% of soft-tissue-condition cases under group health plans were shifted to workers’ compensation, total workers’ comp costs would increase by $225 million in California alone. Providing two other examples, the institute said the comparable figures would be $100 million in Pennsylvania and $25 million in Iowa.