Frequently Asked Questions about Impairment Ratings

This article is intended for RateFast users who have questions about the Whole Person Impairment ratings that come with each PR-4 Permanent & Stationary work injury report.

This FAQ contains answers to a few common questions that we’ve received regarding RateFast impairment ratings.

We pride ourselves in the accuracy of our impairment ratings, and would be happy to explain how they are being calculated. If your question isn’t answered here, then please contact us with questions about your PR-4 report.

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Attorneys in Workers’ Comp: Who they are, what they do, and when to get one

Roles that Defense and Applicant Attorneys play in Workers’ Comp: A historical perspective

Many workers’ compensation claims today involve an attorney at some point. The work comp system, when it came to the United States from Germany, was supposed to be simple, transparent and efficient—a system without attorneys or judges, that focused on three simple steps: 

  1. Medical treatment
  2. Patient recovery
  3. Patient’s return to work

Any permanent impairment would be measured by a doctor with a simple formula, and would tell you how much that injury was worth. 

Permanent disability, on the other hand, was originally used to measure the amount of machines the worker could no longer operate.  The amount of compensation that the injured worker received would then come from that loss.

So, how did work-comp become one of the most complicated areas of law?

Why are defense attorneys involved in today’s workers’ compensation system? There are two primary reasons why attorneys need to get involved: 

This, in turn, results in: 

  • Increased cost of the claim.
  • Increased amount of medical treatment ultimately provided.

And, finally, that an injured worker seeks out an attorney.  This can then further result in additional body parts being added to the claim.  Therefore, providers should always be asking themselves:

“How do I get this case accurately resolved, in the fastest amount of time?” 

When this doesn’t happen, lawyers get involved.

Related Reading

“When should an injured worker get an attorney?”

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Carpal Tunnel Syndrome: What it is and how to measure it

This article is intended for medical providers and others who are interested in carpal tunnel syndrome that is caused by workplace activity.Carpal Tunnel Syndrome

What is carpal tunnel syndrome, exactly?

Carpal tunnel syndrome, or CTS, is caused by pressure on the median nerve in your wrist. The median nerve travels from the forearm through the carpal tunnel into the hand.

What are the symptoms of CTS?

  1. Numbness
  2. Tingling
  3. Weakness
  4. Shooting pain

For further reading on the symptoms of CTS, check out this Mayo Clinic article.

How often does CTS occur?

A lot. According to the American Academy of Family Physicians, Carpal Tunnel Syndrome (CTS) occurs in approximately 3-6% of the adult population.

While CTS can be caused by genetics, diabetes, and pregnancy one major factor can be repetitive, forceful movement. As a result, CTS is a very common workplace injury.

How to measure CTS for an impairment rating

When CTS is caused by work related activities, and if an employee is permanently impaired due to CTS, then the condition requires an impairment rating.

Like all injuries, calculating an accurate impairment rating for CTS requires measurements that can be reproduced. In other words, it’s important the medical providers measure CTS in their patients multiple times to ensure that another provider would obtain the same measurements.

In California (and many other states), all impairment ratings for work-related injuries should be calculated according to the AMA Guides, 5th edition.

According to the Guides, the objective factors that affect the PR-4 impairment rating include sensory loss, grip and pinch loss, and loss of range of motion.

If you’ve used RateFast to write a PR-4 report for an injury to your patient’s wrist, then you probably remember being prompted to measure each of these factors.

CTS Factors and Measurement Tools

  • Sensory loss should be measured with two-point discrimination and monofilament testing using the Semmes Weinstein monofilaments.
  • You can measure grip and pinch loss with a dynamometer.
  • Measure the patient’s loss of range of motion with a goniometer. (Check out the RateFast Goniometer app, available for iOS and Android.)

Remember to use the proper devices to take all measurements twice to make sure your findings are compliant with the AMA Guides. When medical providers don’t take multiple measurements, then their PR-4 report will be incomplete. The result is often an inaccurate impairment rating—which can result in happy insurance carriers and unhappy patients.

How to measure range of motion for a PR-4 report

If your patient has injured a joint, then you (the medical provider) should be sure to measure the range of motion (ROM) of that joint. It’s particularly important to report the range of motion of an injured joint in a PR-4 Report (or the PRIMARY TREATING PHYSICIAN’S PERMANENT AND STATIONARY REPORT).


Measuring the range of motion for an injured joint is essential for calculating an accurate impairment rating.

If you don’t know how much motion your patient has lost, then you can’t tell how much the work injury impaired him or her.

4 Steps to taking accurate range of motion (ROM) measurements for work comp

1. Have your patient warm up by stretching for two minutes

If your patient warms up before measuring, then your measurements  will be more accurate and consistent, with greater reproducibility.

Reproducibility of measurements within 10% is necessary for measurements to be considered valid by the AMA guides.

2. Use the proper tool

If the joint is in the upper or lower extremity (arm or leg), then use a goniometer.

If the injured joint is in the spine, then use an inclinometer.

3. Measure both sides

Notice that the PR-4 report says “Include bilateral measurements – injured/uninjured – for injuries of the extremities.”

So, if your patient has injured her right shoulder, then measure the range of motion of both shoulders. This shows the contrast between the injured body joint and the uninjured joint.

Unless, of course, both sides are injured! But in this case, you should still measure both sides and report your measurements.

4. Measure multiple times!

If the injured joint is in the upper extremity, then take two measurements across each plane (flexion, extension, etc.).

If the injured joint is in the lower extremity or the spine, then take three measurements across each plane.

5. Report your results in the “Physical Examination” section of the PR-4 report

You will find the “Physical Examination” section on the second page of the PR-4 report form that’s currently on the California Department of Industrial Relation’s website.

Make sure that you present your measurements clearly so that it’s easy to read for a claims adjuster, employer, or another doctor. Indicate the plane of motion and the side of the measurement.

We like to show our measurements in a table. This is how the new version of RateFast, our PR-4 reporting web app, displays the range of motion of a body part:

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AMA Guides 5ed Glossary Definitions (Pages 599-603)

AMA Guides 5ed Glossary Definitions (Pages 599-603)

Below is a common list of terms that help RateFast users better understand the basics definitions used for impairment ratings. You will find many of these terms used in RateFast to provide more consistent and reproducible reports.


A factor(s) (eg, physical, chemical, biological or medical condition) that adversely alters the course or progression of the medical impairment. Worsening of a preexisting medical condition or impairment.


Fixation of a joint in a specific position by disease, injury or surgery. When surgically created, the aim is to fuse the joint in that position, which is best for improved function.


A distribution or allocation of causation among multiple factors that caused or significantly contributed to the injury or disease and existing impairment.

Assistive devices

Devices that help individuals with a functional loss increase function. Examples include reachers, extended grabbers, hearing aids, and telephone amplifiers.


An identifiable factor (eg. accident or exposure to hazards or disease) that results in a medically identifiable condition.

Chronic pain

Pain that extends beyond the expected period of healing or is related to a progressive disease. It is usually elicited by an injury or disease but may be perpetuated by factors that are both pathogenically and physically remote from the original cause. Because the pain persists, it is likely that environmental and psychological factors interact with the tissue damage, contributing to the persistence of pain and illness behavior.

Combined Values Chart

A method used to combine multiple impairments, derived from the formula A+ B(1-A) w combined values of A and B, which ensures that the summary value will not exceed 100% of the whole person.


A permanent shortening (as of muscle, tendon, or scar tissue) producing loss of motion, deformity, or distortion.

Desirable weight

A range of optimal weight given an individual’s sex, age, height and body habitus.


Alteration of an individual’s capacity to meet personal, social, or occupational demands or statutory or regulatory requirements because of an impairment. Disability is a relational outcome, contingent on the environmental conditions in which activities are performed.

Effects of medication

Medication may impact the individual’s sign, symptoms, and ability to function. They physician may choose to increase the impairment estimate by a small percentage (1% to 3%) to account for effects of treatment.

Functional limitations

The inability to completely perform a task due to an impairment. In some instances, functional limitations may be overcome through modifications in the individual’s personal or environmental accommodations.


A historical term used to describe disability or a person living with a disability or disabilities. A handicapped individual has been considered to be someone with a physical or mental disability that substantially limits activity, especially in relation to employment or education.


A loss, loss of use, or derangement of any body part, organ system, or organ function.

Impairment evaluation

A medical evaluation performed by a physician, using a standard method as outlined in the Guides, to determine permanent impairment associated with a medical condition.

Impairment percentages or ratings

Consensus derived estimates that reflect the severity of the impairment and the degree to which the impairment decreases an individual’s ability to perform common activities of daily living as listed in Table 1-2.


A conscious and willful feigning or exaggeration of a disease or effect of an injury in order to obtain specific external gain. It is usually motivated by external incentives, such as receiving financial compensation, obtaining drugs, or avoiding work or other responsibilities.

Maximum medical improvement (MMI)

A condition or state that is well stabilized and unlikely to change substantially in the next year, with or without medical treatment. Over time, there may be some change, however, further recovery or deterioration is not anticipated.


A range or zone that represents healthy functioning and varies with age, gender, and other factors, such as environmental conditions.


An unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage.


A sensation of prickling, tingling, or creeping on the skin, usually associated with injury or irritation of a sensory nerve or nerve root.

Permanent impairment

An impairment that has reached maximal medical improvement.


An artificial device to replace a missing part of the body.


Any pathological condition of the nerve roots.


A return of the disorder or disease after a remission.


Synonymous with reliability. Consistency in results when examinations (tests) are repeated.


Pain along the course of a sciatic verve, especially in the back of the thigh, caused by compression, inflammation, or reflex mechanisms.


A radiographic method used to determine actual limb length.


The action or manner of treating an individual, medically or surgically. Medical treatment is the action or manner of treating an individual, medically or surgically by a physician. Treatment may include modalities recommended by a health care provider.


An accurate measurement apart from random errors. Validity refers to the extent to which a test measures what it is intended to measure.

Whole person impairment

Percentages that estimate the impact of the impairment on the individual’s overall ability to perform activities of daily living, excluding work.

Workers’ compensation

A compensation program designed to provide medical and economic support to workers who have been injured or become ill from an incident arising out of and in the course of their employment.

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Effects of Medication and Impairment Rating

How the AMA Guides 5th Edition approaches impairment is complex, and accurate impairment ratings are tricky as a result.

For example, many medical providers don’t realize that the effects that medication has on an injured worker can actually change the worker’s impairment rating. This is defined on page 600 of the AMA Guides.

With page after page of definitions and tables, little details like these can easily be glossed over. We designed RateFast so that you don’t need to spend your time reading and re-reading the Guides. If you use RateFast to write your California PR-4 reports, then our software will prompt you with easy-to-answer questions about the effects that medication has on your patient.

But it’s still important to understand how the effects of mediation impact a worker’s whole person impairment. Here are a few key facts:

  1. “Effects of medication” are defined on page 600 of the AMA Guides, 5th Edition: “Medications may impact the individual signs, symptoms, and ability to function.”
  2. If an injured worker is affected by the medication he or she takes for the work-related injury, then the physician may choose to increase the impairment by small amount—between 1% and 3%. (Frustratingly, the AMA Guides do not give specific instructions on how to do this.)

So imagine that your patient has reached MMI for an injury to the low back. Let’s say that she is assigned a DRE category II and given a 5% WPI.

Now, imagine that the muscle relaxant she has been prescribed causes excessive drowsiness and limits her ability to drive. Is she eligible for an increased whole person impairment rating? Yes. The muscle relaxant has affected her life by limiting her ability to drive.

The moral of the story: if you’re a medical provider, make sure to ask your patients if their medications cause any side effect. It could make a real change in their impairment rating.

If you need help remembering to ask if medications are affecting your patients symptoms, try RateFast today for free. This question is built into our patient history questionnaire and our impairment calculations.

Do you have all the tools you need to perform an impairment exam?

Doctors can’t calculate an accurate impairment rating without the proper tools. Here at RateFast, we’ve reviewed a lot (a lot) of impairment ratings, and in our experience, one reason why doctors produce incorrect unjustifiable ratings is because they did not take the necessary measurements.

Accurate impairment ratings require accurate measurements, and to get the right measurements, you need the right tools.

Tools to Calculate Impairment Ratings

  1. Height and weight scale and blood pressure cuff — You need basic measurements and the worker’s basic vital signs.
  2. Tape measure — Made of flexible material, like fabric.
  3. Goniometer — Used for measuring joint ranges of motion. We prefer using goniometer apps on our phones. If you have an Android phone, you can download the RateFast Simple Goniometer for free from the Google Play store. If you have an iPhone, check the Apple App Store soon!
  4. Inclinometer — An inclinometer is used to measure the spine ranges of motion. You can also use use two phone goniometers, or one digital master/slave inclinometer.
  5. Grip dynomometer — Here in California, this is only for pain-free cases, greater than one year from date of injury or surgery.
  6. Pinch dynomometer — Like the grip dynomometer, this is only for pain-free cases, greater than one year from date of injury or surgery.
  7. Monofilament set — Be sure to have a 10 gram member in the set.
  8. Two point nerve discriminator — You can use a bent paperclip measured to 6 mm distance.

That does it. Once you get these tools, you’ll be ready to gather the correct measurements for your impairment ratings like a pro.

What about the rating itself?

Of course, to actually calculate the impairment rating in California (and many other states), you’ll also need the A.M.A. Guides 5th Edition. Then, you’ll need some time to plow through all the tables, diagrams, and charts.

Alternatively, you can join RateFast, and let our impairment rating specialists calculate the rating for you.

How to Measure and Report Ratable Atrophy According to the AMA Guides, 5th Edition

If you’re a medical provider, then at some point in your career you will probably observe atrophy in one of your workers’ compensation cases. We hope this post is useful for you if one of your patients has atrophy that is related to a work injury.

Muscle atrophy is a medical term that is used to describe the loss of muscle size or mass when concerning orthopedic injuries or conditions. For more on the definition of atrophy, click here.

Today, we’re discussing ratable atrophy, as defined by the AMA Guides, 5th Edition.

According to Chapter 15, The Spine (page 382), ratable atrophy in the spine requires a 1 centimeter (cm) difference or greater in the arm, forearm or leg (calf), and 2 cm or greater in the thigh.

Chapter 17, The Lower Extremities, page 530 Table 17-6 allows rating values to be assigned for 1 cm or grater for the thigh or calf.

Make sure muscle atrophy measurements are reported in centimeters. If they are entered in inches, convert and round the value to the nearest centimeter (cm).

Make sure that ratings assigned for muscle atrophy are reported and provided for the injured side.

Make sure that you’re using the correct chapter (Chapter 15, The Spine or Chapter 17, The Lower Extremities) when impairment values for thigh muscle atrophy are being assigned. If you don’t use the correct chapter of the AMA Guides when assigning ratable atrophy, then the impairment rating will be wrong!

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How to Calculate an Impairment Rating for a Skin Condition

Does Impairment Rating Get Under Your Skin?

Today we Chapter 8 in the AMA Guides 5th Edition: “The Skin.” Specifically, we want to make sure that you place a skin condition in the appropriate class for impairment rating.

The rating table, found on page 178 of the Guides, represents the rating strategy for the entire “Skin” chapter. The rating method is a class based rating system comprised of 5 classes. The whole person impairment range for the chapter is 0-95%.

The rating method in this chapter is primarily driven by the impact of the skin condition on activities of daily living (ADL;Table 1-2 Page 4).

Inventory the Activities of Daily Living!

Initial classification of the skin condition is based on determining how many ADLs (activities of daily living) are “limited.” The ADLs that are considered to be limited by the industrial injury or condition are then grouped into the following categories:

  1. No (none)
  2. Few
  3. Many
  4. Most

Classes 3 and 4 are differentiated by “intermittent confinement at home or domicile.”


When creating or reviewing an impairment rating for the injured employee’s skin, make certain the ADLs have been properly reviewed. It is necessary that those ADLs used to classify the rating category clearly are indicated as “limited.” When “Many” ADLs are reported as “limited,” a statement should be included if the condition results in the individual being confined to his or her home.

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