Generally, "by accident" means an "unlooked for" mishap or untoward event that is not expected or designed. Some jurisdictions draw a distinction between the "unlooked for" cause and the "unlooked for" result. (WCxKit)

For example, in Shay v. Rowan Salisbury Schools, 2010 N.C. App. LEXIS 1310 (July 20, 2010), a divided Court of Appeals of North Carolina reversed an award of benefits to a teacher whose knee "gave out" as she ascended the stairs to her classroom. Noting that there was nothing on the stairs that cause the injury and that the teacher had neither slipped nor lost her balance, the court relied upon prior decisions within the state that required an accidental event, not an accident result (the unanticipated injury).See Ch. 42 of “Larson's Workers Compensation Law” (WCxKit).

Other notable events and articles can be found at the Lexis Nexis Workers Compensation Community. 
  
 Copyright 2010 LexisNexis. All rights reserved. This material is excerpted from Larson’s Workers Compensation Law. Reprinted with permission.