Knee Injuries

The knee is structurally the worst-rated of the major body parts in California, and it is worth understanding why before you conclude something went wrong with your case.

The conversion is brutal. Knees are rated in lower extremity percent, converted to whole person at 100% lower extremity = 40% whole person. A "20% lower extremity impairment" is 8% whole person.

And the schedule compounds it. For injuries before 2013, the knee carries the lowest earning-capacity rank of the major body parts — rank 2, against 7 for the shoulder, 5 for the lumbar spine, and 4 for the wrist.

Two structural disadvantages stacked on the same body part. That is not your evaluator's doing.

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:

• Arthritis cannot be combined with range of motion, atrophy, strength, or gait.
• Atrophy, strength, and gait derangement are mutually exclusive with each other.
• Gait derangement stands entirely alone and is a last resort, used only when nothing else applies.

So a worker with a meniscectomy, quadriceps atrophy, a 15-degree flexion deficit, and joint space narrowing cannot collect all four. The evaluator has to choose — and choosing correctly is the whole case.

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.

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

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.

Which is why the single most valuable question in a knee case is whether the evaluator took standing x-rays and actually measured the cartilage interval. A normal knee measures about 4 mm; a 2 mm interval rates 20% lower extremity — 8% whole person, which is eight times what a meniscectomy is worth.

If your knee has arthritic changes and nobody measured the joint space on weight-bearing films, that is a real gap.

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. Most consumer content has never heard of 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 Escobedo, an apportionment opinion that names a condition and attaches a percentage without explaining how and why is not substantial evidence.

And the useful questions are the same: did the evaluator review pre-injury records? Was there any prior treatment, complaint, or restriction? Were you doing your full job the day before? What supports 50% rather than 20%?

The jobs that cause it

Knee cumulative trauma comes from kneeling, squatting, stair and ladder climbing, and prolonged standing on hard surfaces:

Flooring installers, tile setters, carpet layers, plumbers, and roofers. Warehouse workers climbing racks and chassis. Nurses and caregivers. Hotel housekeepers cleaning tubs and reaching under beds. Janitors on restroom detail. Firefighters and law enforcement on stairs. Agricultural field work. Restaurant and kitchen staff standing ten hours on concrete.

How cumulative trauma claims work.

Frequently asked questions