Patrick Fontana twisted his left knee last spring while hitting a drive down the fairway on a golf course in Columbus, Ohio. But what really pained him was the $900 bill for diagnostic imaging ordered by his doctor. Mr. Fontana, a 42-year-old salesman, has a high-deductible health plan coupled to a health savings account. Since he was nowhere near meeting his deductible, he was on the hook for the entire bill.So he did something that insurance companies routinely do: he forwarded the bill to a claims adjuster, in this case My Medical Control, a Web-based company that reviews doctor and...