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- The conversion is brutal. Knees are rated in lower extremity percent, converted at 100% lower extremity = 40% whole person. A “20% lower extremity impairment” is 8% whole person.
- And for injuries before 2013, the schedule compounds it: the knee carries one of the lowest earning-capacity ranks in the schedule — rank 2, shared with the elbow and ankle and above only the hand and fingers at rank 1, against 7 for the shoulder, 5 for the lumbar spine, and 4 for the wrist. For injuries on or after January 1, 2013, the law replaced that adjustment with a flat 1.4 factor.
- The single most valuable question in a knee case is whether the evaluator took standing x-rays and actually measured the cartilage interval. A 2 mm interval rates 8% whole person — eight times what a meniscectomy is worth.
What follows is the arithmetic that produces a low knee number, the rule that works in your favor when more than one method applies, the footnote that saves a chondromalacia case, what a replacement is actually scored on, and the two apportionmentApportionment Dividing permanent disability between industrial and non-industrial causes. It is to disability, not to findings on an image. arguments to expect.
The methods, and the trap
Chapter 17 of the AMA Guides offers thirteen ways to evaluate a lower extremity — diagnosis-based estimates, range of motion, arthritis measured by cartilage interval, muscle atrophy, strength, gait derangement, and others. But they cannot simply be stacked. The Guides include a table specifically to prevent double-counting, and its rules are strict.
THE RULE THAT WORKS IN YOUR FAVOR
Where more than one method applies, the Guides direct that the method producing the higher rating be adopted. That is not an argument. That is the chapter’s own instruction.
ARTHRITIS STANDS APART
Arthritis cannot be combined with range of motion, atrophy, strength, or gait.
THREE ARE MUTUALLY EXCLUSIVE
Atrophy, strength, and gait derangement are mutually exclusive with each other.
GAIT DERANGEMENT IS A LAST RESORT
It stands entirely alone, and is used only when nothing else applies.
WHICH MEANS THE EVALUATOR HAS TO CHOOSE
A worker with a meniscectomy, quadriceps atrophy, a 15-degree flexion deficit, and joint space narrowing cannot collect all four. Choosing correctly is the whole case.
Which means an evaluator who computes arthritis at 8% whole person and a diagnosis-based estimate at 1%, and reports the 1%, has misapplied the chapter. That is a straightforward error, not a difference of opinion — and it is checkable.
What the numbers actually look like
| PRESENTATION | TYPICAL WHOLE PERSON IMPAIRMENT |
|---|---|
| Sprain or contusion, resolved | 0% |
| Chondromalacia with crepitus and normal x-rays | 2% — see the footnote below |
| Partial meniscectomy, good result | about 1% |
| Meniscectomy with joint space narrowed to 2 mm | 8% |
| ACL reconstruction with mild residual laxity | about 5% |
| Patellofemoral replacement | 9% |
| Total knee replacement — good result | 15% |
| Total knee replacement — fair result | 20% |
| Total knee replacement — poor result | 30% |
If your knee has arthritic changes and nobody measured the joint space on weight-bearing films, that is a real gap.
Notice the gap. A meniscectomy is worth about one percent. A knee replacement is worth fifteen to thirty. There is almost nothing in between except the arthritis measurement. A normal knee measures about 4 mm; a 2 mm interval rates 20% lower extremity — 8% whole person.
The footnote almost nobody applies
The arthritis table carries a special provision: direct trauma, plus patellofemoral pain, plus physical crepitation, plus no joint space narrowing = 2% whole person.
That is the only place in the entire chapter where kneecap pain with clean x-rays gets a number. Without it, a worker with genuine post-traumatic patellofemoral pain and audible crepitus is rated at zero. Most evaluators never apply it. If that is your knee, ask.
One more rule worth knowing. Where a knee has damage in more than one compartment, only the compartment with the greatest impairment is used. They are not added.
What surgery does
A partial meniscectomy is worth about 1% whole person. That surprises people more than any other number in this area, and it is correct.
A total knee replacement is scored on a hundred-point scale — pain, range of motion, and stability, with deductions for flexion contracture, extension lag, and malalignment — and the score determines whether the result is rated good (15%), fair (20%), or poor (30%).
Which means the post-operative assessment matters enormously. A replacement that leaves you with pain, instability, or a flexion contracture should not be scored as a good result, and the difference between good and poor is double the impairment.
The apportionment fight
Expect two arguments: pre-existing arthritis and obesity. Both have more support in the treatment literature for knees than the equivalent arguments do for shoulders — the guidelines themselves discuss body weight as a risk factor for knee osteoarthritis. We are not going to pretend otherwise.
What still has to be proved is the same thing as always: that the non-industrial factor caused a percentage of the disability, explained with reasoning rather than asserted with a number. Under EscobedoEscobedo The en banc decision requiring an apportionment opinion to explain how and why. A percentage without reasoning is not substantial evidence., an apportionment opinion that names a condition and attaches a percentage without explaining how and why is not substantial evidenceSubstantial evidence The standard a medical opinion must meet to support a finding..
- Did the evaluator review pre-injury records? — An opinion built without them is built on assumption.
- Was there any prior treatment, complaint, or restriction? — Asymptomatic degeneration is not disability.
- Were you doing your full job the day before? — That fact is evidence about what the pre-existing condition was actually costing you.
- What supports 50% rather than 20%? — The percentage has to be explained, not asserted.
The jobs that cause it
Knee cumulative traumaCT — Cumulative trauma Injury from repeated exposure over time. The largest injury category in California and the least claimed. comes from kneeling, squatting, stair and ladder climbing, and prolonged standing on hard surfaces.
FLOORING AND TRADES
Flooring installers, tile setters, carpet layers, plumbers, and roofers — kneeling work, all day, on hard surfaces.
WAREHOUSE AND TRANSPORT
Warehouse workers climbing racks and chassis.
CARE AND CLEANING
Nurses and caregivers. Hotel housekeepers cleaning tubs and reaching under beds. Janitors on restroom detail.
PUBLIC SAFETY, FIELD AND KITCHEN
Firefighters and law enforcement on stairs. Agricultural field work. Restaurant and kitchen staff standing ten hours on concrete.
Frequently asked questions
My rating is 8%. My knee is destroyed. How?
Partly the conversion — 20% lower extremity is only 8% whole person — and, for an injury before 2013, partly the schedule, which treats the knee less generously than the shoulder or spine.
I had a meniscectomy. What’s it worth?
About 1% whole person on its own. If there is joint space narrowing, the arthritis measurement is worth substantially more — and it requires standing x-rays.
I had a knee replacement.
15%, 20%, or 30% whole person depending on how the result scores on pain, motion, and stability. The post-operative assessment is worth arguing about.
My x-rays are normal but my kneecap hurts constantly.
There is a specific provision covering exactly that — direct trauma, patellofemoral pain, crepitus, no narrowing — worth 2%. It is rarely applied.
They said my weight caused it.
That argument has real support in the literature, and it still has to explain how and why it caused a specific percentage of your disability.
Can they add up all my knee problems?
No. The methods are mutually exclusive in defined ways. But where more than one applies, the higher rating governs — and that rule is frequently not followed.
Sources
Labor Code § 4660.1 (permanent disability for injuries on or after 1/1/2013)§ 4658(d)(1), (e) (percentage to weeks)§ 4663 (apportionment to causation)8 CCR § 9805 (adoption of the 2005 Permanent Disability Rating Schedule, which incorporates the AMA Guides, 5th Edition)AMA Guides 5th Ed. ch. 17 (the lower extremities)Escobedo v. Marshalls (en banc). Impairment values are summarized, not reproduced; your rating depends on your own examination findings.
General information about California law, not legal advice about your case.
Impairment values described are from the AMA Guides, 5th Edition as applied under the California rating schedule; the Guides are a copyrighted medical text and figures here are summarized rather than reproduced. Your rating depends on your own examination findings.
Reviewed by Jamey Teitell, Partner & Trial Attorney · Last reviewed
Law Offices of Solov & Teitell, APC · (213) 380-9310
Printed from https://www.solovteitell.com/injuries/knee/ · Last reviewed