Workers’ Compensation · Primary-source case analysis

Benson: Successive Injuries Generally Require Separate Causation-Based Disability Awards

By Aneeta Mishra and Timothy Chan

Published May 21, 2026

Dianne Benson v. The Permanente Medical Group addressed two neck injuries that became permanent and stationary together and an agreed examiner’s equal causation allocation.

SB 899 changed the governing premise

Sections 4663 and 4664 made causation the basis for apportionment and limited each employer’s liability to disability directly caused by the injury.

Separate injury analysis became the rule

Each specific or cumulative injury ordinarily required its own causation finding and permanent-disability award.

All contributing causes had to be considered

The analysis included current, prior, and subsequent industrial injuries as well as nonindustrial conditions.

A narrow combined-award possibility remained

A combined award could still be justified only where physicians could not parcel causal percentages with reasonable medical probability.

Key takeaways

• List every claimed injury and affected body part.
• Require medical reasoning for each causal percentage.
• Distinguish disability causation from injury causation.
• Explain specifically if reliable allocation is medically impossible.