38 C.F.R. § 4.18
A veteran may be considered as unemployable upon termination of employment which was provided on account of disability, or in which special consideration was given on account of the same, when it is satisfactorily shown that he or she is unable to secure further employment. With amputations, sequelae of fractures and other residuals of traumatism shown to be of static character, a showing of continuous unemployability from date of incurrence, or the date the condition reached the stabilized level, is a general requirement in order to establish the fact that present unemployability is the result of the disability. However, consideration is to be given to the circumstances of employment in individual claims, and, if the employment was only occasional, intermittent, tryout or unsuccessful, or eventually terminated on account of the disability, present unemployability may be attributed to the static disability. Where unemployability for pension previously has been established on the basis of combined service-connected and nonservice-connected disabilities and the service-connected disability or disabilities have increased in severity, § 4.16 is for consideration.
38 C.F.R. §4.18