The S&P 500 lost 0.9% while the Health Care sector (XLV) showed little movement during trading today.

Onyx Pharmaceuticals (ONXX) was a major gainer in the sector, rising 11.7% (+$7.98) to close at $76.38 with 9.4 million shares moving. The stock traded in a range of $70.12 to $79.20. Align Technology (ALGN) and Alimera (ALIM), in the same sector, also saw major gains today.

Sirona Dental Systems (SIRO) declined 4.1% to close at $44.10, moving below its 50-day moving average of $44.10 and 200-day moving average of $46.45.

Abaxis (CRVL) fell 5.3% to close at $37.27, moving closer to its 50-day moving average of $36.40. Also, the stock moved closer to its 200-day moving average of $45.25.

Intuitive Surgical (ISRG) was one of the sector's big losers, as its price dropped 8.4% (-$45.71) to close at $498.50. 1.5 million shares of the stock moved. The stock traded in a range of $494.55 to $518. The stock has fallen over the last three months, dropping $61.61 (-11%) from $560.11 on April 24, 2012.