Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Hanger Orthopedic Group (NYSE: HGR), the largest owner of orthopedic patient-care centers in the U.S., soared today, gaining as much as 23% after the company reported fourth-quarter results.

So what: On a reported basis, Hanger's fourth quarter was pretty ugly; earnings per share fell from $0.37 in 2009 to $0.02. However, the lower profit was due to expenses related to moving the company's headquarters, refinancing debt, terminating an interest rate swap, and making an acquisition. Excluding those costs, the company's adjusted profit per share was $0.52. Even if we back out a $0.06-per-share tax benefit in the quarter, the adjusted earnings easily topped the $0.40 that analysts were expecting. Revenue for the quarter was up 10% from 2009 and was slightly above Wall Street's estimates.

Now what: Hanger has been a steady grower as it continues to build its footprint around the U.S., and the company sees that continuing in 2011. Management provided per-share earnings guidance in a range of $1.63 to $1.68, above the $1.58 analysts had estimated. At the midpoint of its revenue guidance, revenue would grow 16% in 2011, and it's also targeting a 20-40 basis point increase in its operating margins. The company's stock currently trades at just less than 17 times the midpoint of 2011 earnings guidance, which means that if the company is able to continue to execute as it has in the past, shares look pretty reasonably valued.

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Fool contributor Matt Koppenheffer does not own shares of any of the companies mentioned. You can check out what Matt is keeping an eye on by visiting his CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool or on his RSS feed. The Fool's disclosure policy prefers dividends over a sharp stick in the eye.