A physician must determine the approximate percentage of the disability that is due to the current job-related injury. That percentage determines the amount for which the current employer is liable. This is known as apportionment. Generally, the concept of medical apportionment assigns a percentage of an employee’s permanent impairment to the work itself and the remaining percentage to other factors, including prior injuries.

A California Supreme Court ruling confirms the proper calculation of a workers’ compensation permanent disability award for employees who suffer multiple injuries. The California Supreme Court, in Brodie v. WCAB, clarified conflicting court opinions when the employee’s overall disability is subject to apportionment.1

After reviewing legislative history and cases analyzing this issue, the court rejected findings in prior cases that used different formulas and approved the formula that was used in Fuentes v. WCAB. 2 The Supreme Court ruling requires the calculation of apportionment to begin with the overall percentage of permanent disability and then subtract the non-compensable percentage of permanent disability (e.g., the percentage of the disability that is attributable to a previous injury).

Brodie ensures that employers only bear liability for the percentage of permanent disability that was directly caused by the current work-related injury. Employees with pre-existing conditions or prior industrial injuries should only receive workers’ compensation in an amount commensurate with the injury that has just occurred.

Apportionment rules apply only to liability for permanent disability benefits. Temporary disability benefits and medical costs cannot be apportioned to prior injuries or conditions to lessen the employer’s liability for these benefits. The result is that the employer pays temporary disability and medical treatment costs in full even when the need for such is just partially caused by the work-related injury.

1. Brodie v. WCAB, 40 Cal. 4th 1313 (2007)