N.C. Gen. Stat. § 97-33: Prorating in event of earlier disability or injury.

If any employee is an epileptic, or has a permanent disability or has sustained a permanent injury in service in the United States Army or Navy, or in another employment other than that in which he received a subsequent permanent injury by accident, such as specified in G.S. 97-31, he shall be entitled to compensation only for the degree of disability which would have resulted from the later accident if the earlier disability or injury had not existed. (1929, c. 120, s. 33; 1975, c. 832; 2011-183, s. 127(b).)