This week, the ratings of three Medical Devices stocks on Portfolio Grader are down. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

This week, Hansen Medical (NASDAQ:HNSN) drops from a D (“sell”) to an F (“strong sell”) rating. Hansen Medical develops and manufactures medical robotics designed for positioning, manipulation, and control of catheters and catheter-based technologies. In Portfolio Grader’s specific subcategories of Earnings Growth, Earnings Momentum, Equity, Cash Flow, and Sales Growth, HNSN also gets F’s. The stock price has fallen 19% over the past month, worse than the 1.2% increase the Nasdaq has seen over the same period of time. As of July 23, 16.5% of outstanding Hansen Medical shares were held short. For a full analysis of HNSN stock, visit Portfolio Grader.

Insulet (NASDAQ:PODD) slips from a C (“hold”) to a D (“sell”) rating. Insulet is a medical device company that develops, manufactures and markets an insulin infusion system for people with insulin-dependent diabetes. The stock also gets an F in Equity. As of July 23, 21.3% of outstanding Insulet shares were held short. For more information, get Portfolio Grader’s complete analysis of PODD stock.

Syneron Medical (NASDAQ:ELOS) also declines from a C to a D rating this week. Syneron Medical designs, develops, and markets aesthetic medical products based on proprietary Electro-Optical Synergy technologies. The stock gets F’s in Earnings Revisions, Equity, and Cash Flow. To get an in-depth look at ELOS, get Portfolio Grader’s complete analysis of ELOS 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.