This week, the overall grades of three Medical Devices stocks are lower, according to the Portfolio Grader database. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

This week, Given Imaging (NASDAQ:GIVN) falls to a D (“sell”), worse than last week’s grade of C (“hold”). Given Imaging has developed a proprietary wireless imaging system that allows a medical professional to examine the gastrointestinal tract. GIVN also rates an F in Portfolio Grader’s specific subcategory of Earnings Surprise. The stock price has dropped 10.8% over the past month, worse than the 3.5% increase the Nasdaq has seen over the same period of time. The stock’s trailing PE Ratio is 35.10. To get an in-depth look at GIVN, get Portfolio Grader’s complete analysis of GIVN stock.

This is a rough week for Greatbatch (NYSE:GB). The company’s rating falls to D from the previous week’s C. Greatbatch develops and manufactures power sources, feedthroughs, and wet tantalum capacitors used in implantable medical devices. The stock gets F’s in Earnings Growth, Earnings Momentum, and Margin Growth.

For a full analysis of GB stock, visit Portfolio Grader.

Tornier (NASDAQ:TRNX) ratings are on the decline this week as the company earns an F (“strong sell”). Last week, it received a D (“sell”). Tornier designs, outsources the manufacture of and markets orthopedic products. The stock gets F’s in Earnings Momentum and Earnings Revisions. For more information, get Portfolio Grader’s complete analysis of TRNX stock.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.