Selecting the correct pain management diagnosis code

The diagnosis establishes the medical necessity for the service.

The logic of ICD-10-CM codes is very different from the organization of Current Procedural Terminology (CPT®) codes. CPT codes tell the payer what you did; ICD-10-CM codes tell why you did it. You should use particular care when selecting diagnosis codes. Always select the most specific code possible, based on the clinician’s documentation. Another difference between CPT and ICD-10-CM is when the new code sets go into effect. CPT codes go into effect on January 1 of the calendar year. ICD-10-CM codes are released at the start of the fiscal year (FY). For example, FY 2023 codes went into effect on October 1, 2022.

Using vague or non-specific diagnosis codes is likely to result in denials. If the source of the pain has been diagnosed, code for the source rather than the symptom. Even when you specifically code for the source, your carrier may still deny the claim based on its particular payment policy. When you spot a pattern of denials, it’s always helpful to verify directly with payers that the problem was diagnosis-related and not a result of questionable medical necessity for the entire treatment plan.

One place to check: Your carrier’s website. Medicare carriers and commercial payers post their payment policies on the Internet. These policies list information about coverage of specific services, including the diagnosis codes that the payer has decided constitute medically necessary conditions for reimbursement of a procedure. It is important to be familiar with the payer or carrier’s policies in order to avoid denials caused by medical necessity. The payer may not allow you to bill the patient when this happens.

Providers should never select a diagnosis code simply to receive payment.

Diagnosis coding guidelines

While it’s impossible to offer a universal set of rules for diagnosis code selection, here are some general guidelines to use as a starting point:

Sometimes, pain will not be the primary diagnosis. Pain is a symptom, not the cause. Symptoms like elbow pain can be secondary diagnoses, but for the primary diagnosis, you want to code the underlying illness or injury, like arthritis, sprain, tennis elbow, etc. The most common unspecified diagnosis is low back pain without any further clarification. When you get that, ask yourself, “What is the cause of the low back pain?” After you determine what it is, use low back pain as a secondary diagnosis to further describe the primary reason for the pain.

Keep these tips in mind when selecting a diagnosis code:

• Designate the post-operative diagnosis wherever possible.
• Avoid repeating the procedure in narrative form in the diagnosis section instead of giving the diagnosis. For example, don’t list a diagnosis description of lysis of adhesions instead of epidural adhesions. Include specifics, such as whether the condition included myelopathy, neuritis, or radiculopathy.
• List a diagnosis for each procedure on the claim form. Procedures are listed in order of value, and diagnoses are listed in a corresponding order. The exception is fluoroscopic techniques: these don’t require a unique diagnosis.
• Similarly, physician dictations should link the procedure with the diagnosis. Documentation is very important. By linking the diagnosis to the procedure in the operative note, it will be easier for your insurance carrier to determine which procedure goes with which diagnosis. For multiple procedures, make sure the first diagnosis equals the first procedure and so forth.
• Do NOT use the terms “rule-out,” “possible,” “probable,” “suspected,” or “working diagnosis.” Payers will deny such claims. Instead, describe the signs, symptoms, or other reasons for the procedure. If a patient has back pain and the physician performs a facet joint injection to determine whether the pain was caused by a facet joint disorder, and the block brought no relief, you’d code the claim as back pain, not rule out facet joint syndrome. If the block does bring relief, a diagnosis of lumbar stenosis might apply. Despite the common usage of the term facet joint syndrome, there is no ICD-10 code for this diagnostic descriptor. However, the notes for ICD-10 codes in the spondylosis series (M47) include degeneration of facet joints.
• Describe the highest degree of specificity available. If a syndrome is referenced, such as facet joint syndrome, describe the related symptoms, such as lumbar stenosis, other spondylosis with myelopathy, lumbar region code (M47.16), or the appropriate lumbar disk degeneration code (M51.36 or M51.37).
• Avoid “not otherwise specified” (NOS) ICD-10 codes. Payers don’t like to pay for unspecified codes, and most claims are denied because the carrier’s definition of what is “medically necessary” does not include NOS codes. While from a medical standpoint, they can still be considered valid, make sure to exhaust all other options before using them because, from a coding perspective, they are commonly recognized as “dump” or “catch-all” codes.

Editor’s note: This article is an excerpt from “2025 Pain Management Coding Answers,” published by DecisionHealth®, a division of HCPro LLC. Pre-order the 2026 edition here.