Lines can be a result of either a defective LCD panel, LVDS cable, or Logic board.
you can test the MacBook Pro with an external display to rule out Logic board.. next step would be to make sure the LVDS cable is not loose, or damaged.. if all looks good.. perhaps test with a new LVDS cable. LCD is usually the last thing to go wrong. but some people are foolish enough to grab the notebook by the display.. pressure on the panel and damage the circuitry.