Updated from 7:09 a.m. EDTHealth care stocks generally have underperformed most other sectors during the last year or two. This underperformance could offer an opportunity for short-squeeze plays from heavily shorted biotechnology, health facilities, pharmaceutical and medical equipment stocks. A short squeeze takes place when a stock's short-sellers are forced to cover their positions quickly when the stock they are betting against starts climbing on positive news. As the short-sellers are forced to cover, the price of the stock often moves even higher. The metric for measuring short-squeeze plays is the short ratio, which represents the number of days it would take a stock's short sellers to cover their positions based on the stock's recent average daily trading volume. Stockpickr has compiled the Top Health Care Short-Squeeze Plays, a list of heavily shorted stocks in the sector that have the potential to climb higher on any positive catalyst. One of the most heavily shorted health care-related stocks is HealthSouth Corp. ( HLS), an inpatient rehabilitation services provider with a short ratio of 40. In 2003, a fraud scheme sent shares plummeting. The company is slated to report its most recent quarterly results on May 7. The stock has a forward price-to-earnings (P/E) ratio of 33 and a P/E-to-growth (PEG) ratio of 6.6. HealthSouth shares are owned by Highfields Capital Management, $8.3 billion hedge fund. Highfields also holds shares of Clear Channel Communications ( CCU), which has a 3 short ratio, Qualcomm ( QCOM), which has a 1.2 short ratio, and PNC Financial Services ( PNC), with a 3 short ratio.