Los Angeles County house prices jumped 12.2 percent in January from the year before, the second-biggest gain among large U.S. metro areas, housing data firm Core-Logic. The increase is the biggest annual price gain in single-family homes since April 2006, figures from the Irvine-based data firm show. Los Angeles County house prices have risen for eight consecutive months. Orange County had the nation’s fourth-highest price increase in January, with single-family homes selling for 11.7 percent more than in January 2012. Prices rose 12.1 percent in the Inland Empire, the third-biggest large metro-area gain in the nation. With these gains, the housing market is poised to enter the spring selling season on sound footing.