A new study advises against seeking medical expertise online. If you do, it warns, at least 20 percent of the time your search will lead you astray.
The study has suggested that half of the top search results actually come from companies that may be trying to sell you something.
In fact, health websites run by nonprofit and educational organizations are usually better than commercial sites.
"Sometimes, it's a good thing for patients to take an active role in their health issues. Sometimes, it creates more problems than it solves," Discovery News quoted Jim Starman, an orthopaedic resident at Carolinas Medical Center in Charlotte, North Carolina, as saying.
To gauge the problem's prevalence, the researchers searched Yahoo and Google for 10 common sports medicine diagnoses, including anterior cruciate ligament (ACL) tears, rotator cuff tears and meniscal tears.
They took the top 10 results from both search engines and had three independent reviewers evaluate the sites for accuracy.
The results revealed a huge amount of variability in the quality of sites that turned up, especially among academic and commercial sites.
Nearly half of the top-10 sites were commercial-some of these sites, including eMedicine and WebMD, were surprisingly good, said Starman.
However, more often, commercial sites were sponsored by companies trying to sell products for diagnosing or treating the condition.
These were less trustworthy, as they promoted their products as the best option without any evidence to support their claims-a full 20 percent of all results fell into this category.
In general, the sites of nonprofit and educational organizations scored the highest.
But even then, it can be hard to tell whether a site is inaccurate, incomplete or outdated, said Gary Schwitzer, publisher of HealthNewsReview.org, a site that monitors the media for inaccurate health information.
In the fast-paced world of health care, following guidelines that are even just five years old can be dangerous, he said.
"One size does not fit all for any of us in health care. A good source leads not so much with how much we know, but is almost as quick to tell you what the unknowns and uncertainties are. We're talking about a science here. Uncertainty is rampant in health care," he said. he study has been published in the Journal of Bone and Joint Surgery.