The markets have been on a roll this year, as the S&P 500's (SNPINDEX:^GSPC) picked up more than 18% year to date. The health-care sector's moved right along with the index in 2013, as many leading medical stocks have seen shares roar higher and reward investors with stellar gains.

Not every stock's joined the party, however. A small but select group of laggards hasn't been able to break into the green in 2013 -- and three members of the S&P have left investors shaking their heads. In the following video, Motley Fool contributor Dan Carroll takes you through the index's three worst medical stocks of the year and examines whether this trio of laggards can turn things around in the year's second half.

Fool contributor Dan Carroll has no position in any stocks mentioned. The Motley Fool recommends Intuitive Surgical and owns shares of Intuitive Surgical and Medtronic. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.