For specific injuries, Section 301 of the Workers’ Disability Compensation Act states:
(1) An employee, who receives a personal injury arising out of and in the course of employment by an employer who is subject to this act at the time of the injury, shall be paid compensation as provided in this act. A personal injury under this act is compensable if work causes, contributes to, or aggravates pathology in a manner so as to create a pathology that is medically distinguishable from any pathology that existed prior to the injury. In the case of death resulting from the personal injury to the employee, compensation shall be paid to the employee’s dependents as provided in this act. Time of injury or date of injury as used in this act in the case of a disease or in the case of an injury not attributable to a single event is the last day of work in the employment in which the employee was last subjected to the conditions that resulted in the employee’s disability or death.
(2) Mental disabilities and conditions of the aging process, including but not limited to heart and cardiovascular conditions and degenerative arthritis, are compensable if contributed to or aggravated or accelerated by the employment in a significant manner. Mental disabilities are compensable if arising out of actual events of employment, not unfounded perceptions thereof, and if the employee’s perception of the actual events is reasonably grounded in fact or reality.
(3) An employee going to or from his or her work, while on the premises where the employee’s work is to be performed, and within a reasonable time before and after his or her working hours, is presumed to be in the course of his or her employment. Notwithstanding this presumption, an injury incurred in the pursuit of an activity the major purpose of which is social or recreational is not covered under this act. Any cause of action brought for such an injury is not subject to section 131.
For occupational diseases, Section 401 of the Workers’ Disability Compensation Act states:
(3.1) As used in this chapter, “disability” means a limitation of an employee’s wage earning capacity in work suitable to his or her qualifications and training resulting from a personal injury or work related disease. A limitation of wage earning capacity occurs only if a personal injury covered under this act results in the employee’s being unable to perform all jobs paying the maximum wages in work suitable to that employee’s qualifications and training, which includes work that may be performed using the employee’s transferable work skills. A disability is total if the employee is unable to earn in any job paying maximum wages in work suitable to the employee’s qualifications and training. A disability is partial if the employee retains a wage earning capacity at a pay level less than his or her maximum wages in work suitable to his or her qualifications and training. The establishment of disability does not create a presumption of wage loss.
(3.2) As used in this chapter:
(a) “Disablement” means the event of becoming so disabled.
(b) “Personal injury” includes a disease or disability that is due to causes and conditions that are characteristic of and peculiar to the business of the employer and that arises out of and in the course of the employment. An ordinary disease of life to which the public is generally exposed outside of the employment is not compensable. A personal injury under this act is compensable if work causes, contributes to, or aggravates pathology in a manner so as to create a pathology that is medically distinguishable from any pathology that existed prior to the injury. Mental disabilities and conditions of the aging process, including but not limited to heart and cardiovascular conditions, and degenerative arthritis shall be compensable if contributed to or aggravated or accelerated by the employment in a significant manner. Mental disabilities shall be compensable when arising out of actual events of employment, not unfounded perceptions thereof, and if the employee’s perception of the actual events is reasonably grounded in fact or reality. A hernia to be compensable must be clearly recent in origin and result from a strain arising out of and in the course of the employment and be promptly reported to the employer.
Section 373 of the Act contains a special definition of disability for retirees. A person is considered a retiree if he or she is receiving a pension or retirement benefit (but not a disability pension) that was paid for by the employer. To be disabled, a retiree must prove that he or she is unable “to perform work suitable to the employee’s qualifications, including training or experience.”