What Is California Labor Code §4660 — Permanent Disability Rating?

What is the AMA Guides 5th Edition that California §4660 requires?

California Labor Code §4660 requires the medical-legal evaluator to apply the AMA Guides 5th Edition (California has not adopted the 6th Edition). The Guides assign a Whole Person Impairment percentage based on anatomic, diagnostic, and functional findings. A lumbar disc herniation treated without surgery commonly rates near 7%–13% WPI; a single-level spinal fusion commonly rates near 25%–28%. The impairment percentage is the starting point of every §4660 rating, not the final number. Related coverage: California back-injury workers' comp statewide pillar.

How does the §4660 occupation adjustment actually work?

Under California Labor Code §4660 and the Permanent Disability Rating Schedule, the WPI percentage is adjusted upward for the worker's occupation when the injury affects the body part the occupation depends on. A California warehouse worker with a lumbar fusion gets a larger occupation adjustment than a desk worker with the same fusion, because the warehouse worker's earning capacity is more directly impaired. Two California workers with the same diagnosis can produce materially different ratings from occupation alone.

How does §4660 interact with §4663 apportionment?

After the §4660 rating produces a permanent disability percentage, California Labor Code §4663 allows the California insurer to argue that part of the disability is attributable to non-industrial causes — pre-existing degenerative disc disease, prior injuries, or natural aging. If a medical evaluator assigns 30% of the disability to non-industrial causes, the indemnity portion is reduced by 30%. California places the burden on the employer; the California Supreme Court held in Brodie v. WCAB (2007) that asymptomatic pre-existing imaging findings alone are a weak basis for apportionment. Statute deep-dive: California Labor Code §4610.5 (Independent Medical Review of UR denials).

How does the §4660 rating convert to actual indemnity dollars?

Under California Labor Code §4660 and California Labor Code §4658, the final permanent disability percentage converts to a number of weeks of indemnity. The number of weeks per percent rises as the percentage climbs — a 30% rating produces about 86 weeks at one rate; a 70% rating produces several hundred weeks plus a life-pension component. The weekly indemnity is calculated from the worker's average weekly wage at the time of injury, subject to the statutory maximum reset annually. A 40% California rating commonly falls in the high tens of thousands; a 70% rating exceeds $100,000. Related coverage: California Labor Code §4906 (workers' comp attorney fees).