The workers' compensation laws of the state of Washington define an injury as "a sudden and tangible happening, of a traumatic nature, producing an immediate or prompt result, and occurring from without, and such physical conditions as result there from." (RCW 51.08.100). An injury is just that — something that happens suddenly at a specific time.
An occupational disease on the other hand is a condition that develops over time as a result of work performed. RCW 51.08.140 defines an occupational disease under the Washington state workers' compensation laws as "such disease or infection as arises naturally and proximately out of employment." Examples of occupational diseases are carpal tunnel syndrome or asbestos lung disease. An office worker who does repetitive typing all day can develop carpal tunnel syndrome. A worker repeatedly exposed to asbestos on the job can develop asbestosis or mesothelioma, a type of lung cancer. An electrician or factory worker who squats, kneels, and crawls frequently can develop knee problems. Conditions such as these are compensable under this state's workers' compensation laws.