Primary Care Coding Alert

These 3 scenarios will help you make the best M15-M19 code choice.

Coding arthritis can be tricky. Part of the reason is because the term “includes over 100 different conditions,” according to the Centers for Disease Control and Prevention (CDC) (Source: www.cdc.gov/arthritis/healthcare/index.html).

But as a primary care coder, you need to be very familiar with coding the condition, as it “affects about 1 in 4 adults,” in the CDC’s estimation. So, we’ve prepared this guide to coding arthritis and added three clinical examples to make your arthritis coding a little easier.

Where to Begin

First, it’s important to know what we are talking about when we use the term “arthritis.” Confusingly, “in the U.S., arthritis is also referred to as ‘osteoarthritis,’ and the terms are used interchangeably,” says Melanie Witt, RN, CPC, MA, an independent coding expert based in Guadalupita, New Mexico.

This explains why “the default for ‘arthritis, unspecified’ is ‘osteoarthritis, unspecified site,’” according to AHA Coding Clinic® for ICD-10-CM (Vol. 3, No. 4, 2016), and why the primary code identified for “Arthritis” in the ICD-10-CM index is M19.90 (Unspecified osteoarthritis, unspecified site). Thus, you would report M19.90 “any time the physician simply indicates the patient has arthritis,” according to Witt.

However, you’ll eventually need to get a lot more specific than that. Here’s how.

Look for Location, Laterality …

Fortunately, the osteoarthritis/arthritis codes are relatively straightforward to use. “Almost all the arthritis and osteoarthritis codes specify both the type and site, and those that don’t tell you the type will still at least tell you the site,” notes Kent Moore, senior strategist for physician payment at the American Academy of Family Physicians.

So, you can begin to narrow down your code choices by looking in your provider’s documentation for the anatomical location of the arthritis, such as the hip (M16.-), the knee (M17.-), the first carpometacarpal joint (the joint at the base of the thumb, coded to M18.-), or other joints (M19.-), and the laterality of the osteoarthritis, such as right, left, bilateral, or unspecified.

Pro coding tip: Some arthritis codes code groups, such as M19 (Other and unspecified osteoarthritis) do not contain codes for bilaterality. Should your provider document that the patient has bilateral arthritis in a specific anatomical location, you should follow ICD-10 general coding guideline I.B.13, which states, in part, “If no bilateral code is provided and the condition is bilateral, assign separate codes for both the left and right side.”

“Accordingly, if primary arthritis occurs bilaterally in a patient’s shoulders, as there is no bilateral code, you would need to report the code for each side with M19.011 [Primary osteoarthritis, right shoulder] plus M19.012 [Primary osteoarthritis, left shoulder],” says Moore.

… and Understand Type

Perhaps the hardest part of arthritis coding is knowing what the different statuses mean, because “ICD-10-CM does not define such terms as ‘primary’ or ‘secondary’ in this context,” Moore notes. But the following definitions of the different conditions will help you pinpoint the correct code:

“Primary arthritis is caused by getting older — there are no known pathological causes. Secondary arthritis is caused by an event in the body, such as obesity, injury, inactivity, genetic predisposition, or inflammation, which causes a breakdown of the cartilage. Post-traumatic arthritis is triggered by an acute joint trauma, which can be brought on by a sports injury, a fall, vehicle accident, or a military injury to the joint,” Witt advises coders.

Coding alert: Remember, “unspecified means that the provider has not documented the cause, and as with all correct coding, unspecified classifications should be avoided — especially if a surgical or medical intervention is planned,” cautions Witt.

Putting it All Together

Take a look at these three scenarios and see if you agree with how we’ve coded them.

1. A 65-year-old female patient complains of pain at the base of both the joints of her right and left thumbs. Your provider determines the pain is located in the patient’s right and left carpometacarpal joints and is due to primary osteoarthritis.

CODE CHOICE: M18.0 (Bilateral primary osteoarthritis of first carpometacarpal joints).

2. An obese 48-year-old male patient complains of joint pain in the right knee. Your provider determines the patient has secondary osteoarthritis in the right knee joint due to the patient’s obesity.

CODE CHOICE: M17.5 (Other unilateral secondary osteoarthritis of knee). Note that the only M17.- codes that specify laterality are the codes for primary or post-traumatic osteoarthritis of the knee. For secondary osteoarthritis of the knee, your only choices are the “other” codes for unilaterality or bilaterality (M17.5), or the unspecified code (M17.9). As the knee (right) and the type (secondary) in this example are specified, and as the patient does not have the pain in both knees, M17.5 is really the only choice you have in this case.

3. A 35-year-old male patient complains of pain in the left ankle. His history indicates that he broke the ankle 18 years earlier while playing high-school football. Your provider determines that the patient has post-traumatic osteoarthritis of the left ankle.

CODE CHOICE: M19.172 (Post-traumatic osteoarthritis, left ankle and foot).