ICD-10 Code Buttock Pain Unspecified

If you have ever tried to find the right code for a patient who simply says, “My buttock hurts,” but you cannot pinpoint the exact cause, you know the challenge. You are not alone. Many healthcare providers and medical coders face this situation daily.

The good news is that the ICD-10-CM system includes a specific code for exactly this scenario. It helps you document the visit accurately while protecting reimbursement.

In this guide, we will walk you through everything you need to know about the ICD-10 code for buttock pain unspecified. You will learn when to use it, how to document it, and what pitfalls to avoid. Let us get started.

What Is the Correct ICD-10 Code for Unspecified Buttock Pain?

The correct code for unspecified buttock pain is M79.18. This code falls under the category “Myalgia, other site.”

M79.18 is a specific code for myalgia (muscle pain) of other specified sites, which includes the buttock. When a clinician cannot determine the exact cause of the pain—whether it is sciatica, a muscle strain, bursitis, or something else—M79.18 becomes the appropriate choice.

Here is a quick breakdown:

Important note: M79.18 is not a “dump code.” It still requires a clinical reason for the pain, even if unspecified. You should use it only when a more specific diagnosis remains unknown after a reasonable examination.

Anatomy of the Buttock: Why It Matters for Coding

To code buttock pain correctly, you need to understand what structures lie in this region. The buttock includes several possible sources of pain:

• Gluteal muscles (maximus, medius, minimus)

• Sciatic nerve

• Sacrum and coccyx

• Hip joint referred pain

• Bursae (fluid-filled sacs that cushion the joint)

Each of these structures has its own set of codes. For instance, sciatica gets a G code (G57.0). Gluteal tendinitis gets an M code (M76.0). If your documentation points to a specific structure, you must use that precise code. If not, M79.18 remains your best option.

“Proper coding begins with proper physical examination. When the source of buttock pain cannot be identified after a good exam, M79.18 is acceptable. But always document why you ruled out other causes.” — Dr. Sarah Jenkins, Family Medicine and Coding Consultant

When to Use M79.18: Clinical Scenarios

Let us look at real-life examples where M79.18 is the correct choice.

Scenario 1: Acute, Nonspecific Gluteal Pain

A 45-year-old patient comes in after a long car ride. He reports diffuse pain in the right buttock. There is no trauma, no radiating pain, and no tenderness over the sciatic notch. Your exam is unremarkable except for mild discomfort on palpation of the gluteal muscle belly. You diagnose “unspecified myalgia, right buttock.”

Correct code: M79.18

Scenario 2: Chronic Pain Without Clear Etiology

A 60-year-old woman with fibromyalgia reports bilateral buttock pain. She cannot localize it precisely. MRI of the lumbar spine and hip are normal. You document “chronic bilateral buttock pain, unspecified cause.”

Correct code: M79.18

Scenario 3: Post-Fall Without Focal Findings

A child falls off a bicycle and complains of buttock pain. X-rays of the pelvis and sacrum are normal. There is no bruising or focal tenderness. You diagnose “buttock contusion?” but cannot confirm. The pain is likely muscular.

Correct code: M79.18 (plus an external cause code if your payer requires it)

M79.18 vs. Related Codes: A Comparative Table

One of the biggest sources of coding errors is confusing M79.18 with other similar codes. Use this table to choose wisely.

Key takeaway: M79.18 is for muscle pain of the buttock when no other specific diagnosis fits. If the pain involves nerves, tendons, bursae, joints, or trauma, you must use the appropriate specific code.

Documentation Requirements for M79.18

Insurance companies and auditors scrutinize unspecified codes. To avoid denials, your clinical documentation must include three essential elements.

1. Location

Document the exact location of the pain. Is it the right buttock, left buttock, or bilateral? The ICD-10 system often requires laterality, but M79.18 does not specify side. However, your note should.

Example of good documentation:
“Patient reports dull ache in the left gluteal region, approximately 5 cm lateral to the sacrum.”

Example of poor documentation:
“Buttock pain.”

2. Quality and Duration

Describe the pain. Is it sharp, dull, burning, or aching? How long has it lasted? Acute (less than 6 weeks) or chronic (over 12 weeks)?

Example:
“Sharp, intermittent pain in the right buttock for three days. No radiation. Aggravated by sitting and walking.”

3. Exclusion of Other Causes

Briefly note why you ruled out more specific diagnoses. You do not need a full novel, but one sentence helps.

Example:
“No tenderness over sciatic notch. Straight leg raise negative. Hip range of motion full and pain-free. Normal lumbar spine exam.”

Common Coding Mistakes and How to Avoid Them

Even experienced coders slip up. Here are the most frequent errors with M79.18.

Mistake #1: Coding M79.18 for Radiating Leg Pain

If the patient’s buttock pain radiates down the leg, you likely have a nerve issue (sciatica). Use M54.30 (sciatica, unspecified side) or the laterality-specific codes.

Mistake #2: Using M79.18 After Trauma

After a fall or direct blow, you should use an injury code from S30 (superficial injury of abdomen, lower back, pelvis, and buttock). For example, S30.00XA for contusion of unspecified buttock.

Mistake #3: Forgetting Laterality in Your Note

Even though M79.18 does not require laterality, payers may ask for it. Always document left, right, or bilateral in the patient’s chart.

Mistake #4: Using M79.18 as a Chronic “Default” Code

If a patient has had buttock pain for six months with no diagnosis, you need to do more investigation. Repeatedly using M79.18 for the same patient without further workup can trigger audits.

How to Sequence M79.18 on a Claim

Proper sequencing matters for medical necessity. Here are common scenarios.

Primary Diagnosis (First-Listed)

Use M79.18 as the primary diagnosis when the chief complaint is buttock pain and no other definitive diagnosis exists.

Example claim:

1. M79.18 (Myalgia, left buttock)

2. Z23 (Encounter for immunization) – if applicable

Secondary Diagnosis

Sometimes, buttock pain is a symptom of another condition. In that case, list the underlying condition first.

Example claim (patient with lumbar radiculopathy):

1. M54.16 (Radiculopathy, lumbar region)

2. M79.18 (Myalgia, bilateral buttocks, secondary to radiculopathy)

Unspecified Buttock Pain in Special Populations

Different patient groups require extra attention when coding M79.18.

Pediatric Patients

Children often cannot localize pain well. A child saying “my bum hurts” could mean anything from constipation to muscle strain to sacroiliitis. Before coding M79.18 in a child, consider:

• Constipation (K59.00) – very common cause of referred buttock pain

• Piriformis syndrome – rare but possible in active children

• Juvenile idiopathic arthritis – inflammatory causes

Coding tip: In children without clear muscular findings, consider using R10.2 (pelvic and perineal pain) instead of M79.18.

Geriatric Patients

Older adults frequently have degenerative changes that cause buttock pain. Do not default to M79.18 without considering:

• Spinal stenosis (M48.06) – often presents with buttock pain while walking

• Hip osteoarthritis (M16.9) – refers pain to the buttock

• Sacral insufficiency fracture (M84.48XA) – common in osteoporotic women

Athletes

Runners and cyclists often report buttock pain. In this population, you can often find a specific cause. Avoid M79.18 if you suspect:

• Hamstring tendinopathy (S76.311A for right, S76.312A for left)

• Piriformis syndrome (G57.01 or G57.02)

• Ischial bursitis (M70.7)

A Helpful List: Steps to Confirm M79.18 Is the Right Code

Before finalizing M79.18, run through this quick checklist:

• Did I examine the lumbar spine? (Rule out radiculopathy)

• Did I check the hip joint range of motion? (Rule out hip pathology)

• Is there any radiation down the leg? (Rule out sciatica)

• Is there tenderness over the greater trochanter? (Rule out bursitis)

• Is the pain exactly over the coccyx? (Rule out coccydynia)

• Did the patient have recent trauma? (Use injury codes)

• Did I document the quality and duration of the pain?

• Did I note laterality (left, right, or bilateral)?

If you answered “yes” to any of the rule-out questions, consider a more specific code. If you answered “no” to all and still have a patient with muscle-type pain in the buttock, M79.18 is appropriate.

What Happens When You Overuse Unspecified Codes?

Payers like Medicare and commercial insurers watch for unspecified code overuse. If you use M79.18 too often, several consequences can occur:

1. Audits – You may receive a records request to justify your coding.

2. Denials – Some payers automatically deny unspecified codes for certain visit types.

3. Downcoding – An auditor may change your code to a lower-paying category.

4. Suspicion of low-quality care – Frequent use of unspecified codes can suggest poor diagnostic effort.

That is why we always recommend specificity whenever possible. M79.18 is a tool, not a crutch.

Clinical Tips to Move Away From “Unspecified”

Sometimes, a few extra minutes of examination can turn an unspecified code into a specific one. Here is how.

Perform the “Buttock Pain Triad” Exam

1. Straight leg raise – If positive, think L5/S1 radiculopathy (M54.16).

2. FABER test (Flexion, Abduction, External Rotation) – If positive, think hip joint or sacroiliac joint (M16.9 or M53.3).

3. Piriformis stretch test – If pain with active resistance to external rotation, think piriformis syndrome (G57.01 or G57.02).

These three tests take less than two minutes and give you a much clearer diagnostic picture.

Consider Imaging If Pain Persists

If a patient returns twice with the same buttock pain and you still use M79.18, consider:

• X-ray of the hip or lumbar spine

• MRI if red flags are present (night pain, fever, weight loss)

• Ultrasound to evaluate for gluteal tendinopathy or bursitis

Document Your Differential Diagnosis

Even if you end up using M79.18, list the conditions you ruled out. For example:

Differential diagnosis considered and excluded:

• Lumbar radiculopathy (normal straight leg raise, no leg symptoms)

• Hip osteoarthritis (normal hip ROM, no groin pain)

• Piriformis syndrome (negative FABER and piriformis stretch tests)

• Sacroiliac joint dysfunction (normal SI joint provocative tests)

This type of documentation protects you during an audit and shows good medical decision-making.

Additional Resources for ICD-10 Coding of Buttock Pain

Link to CMS ICD-10 Official Guidelines for Coding and Reporting:
https://www.cms.gov/medicare/coding-billing/icd-10-codes/2025-icd-10-cm
(Always check the latest version as codes and guidelines update annually.)

Billing and Reimbursement Considerations for M79.18

Reimbursement for unspecified codes varies by payer. Here is what you need to know.

Medicare

Medicare generally accepts M79.18 for office visits (E/M codes 99202-99215) as long as the documentation supports medical necessity. However, Medicare may deny M79.18 for certain physical therapy claims if the plan of care does not clearly address myalgia.

Commercial Insurers

Most commercial payers reimburse M79.18 without issue for primary care and urgent care visits. However, for specialty visits (orthopedics, pain management, neurology), payers expect a more specific diagnosis. An orthopedist repeatedly coding M79.18 may raise red flags.

Workers’ Compensation

Workers’ comp claims require high specificity. If an employee develops buttock pain after lifting, you need to determine if it is a muscle strain (M79.18) or a disc herniation (M51.16). M79.18 is acceptable for the initial visit but not for prolonged treatment.

Average Reimbursement Rates (Illustrative)

Note: Rates vary by region, payer contract, and patient benefits. These are estimates only.

Frequently Asked Questions (FAQ)

1. Is M79.18 the same as “gluteal pain unspecified”?

Yes. Gluteal pain is the medical term for buttock pain. M79.18 is the appropriate code for unspecified gluteal muscle pain.

2. Can I use M79.18 for tailbone pain (coccyx pain)?

No. Coccyx pain (coccydynia) has its own code: M53.3. Use M79.18 only for pain in the fleshy part of the buttock, not the very bottom of the spine.

3. What is the difference between M79.18 and M79.1?

M79.1 is the parent code for myalgia (unspecified site). M79.18 is the more specific child code for “other site,” which includes the buttock. Always use M79.18 for buttock pain, not M79.1.

4. Does M79.18 require a seventh character or laterality?

No. M79.18 does not require a seventh character. Laterality is not built into the code, but you must document the side in your clinical note.

5. How long can I use M79.18 for the same patient?

There is no set time limit, but if the pain persists beyond 4-6 weeks without a specific diagnosis, you should reconsider. Refer to physical therapy, order imaging, or consult a specialist. Using M79.18 for months without further investigation may be considered poor medical practice.

6. Can a chiropractor use M79.18?

Yes. Chiropractors frequently use M79.18 for patients with nonspecific gluteal muscle pain, especially when it is not related to spinal subluxation.

7. What code should I use for buttock pain during pregnancy?

Pregnancy-related buttock pain can be tricky. If it is due to nerve compression from the growing uterus, use O26.89 (other specified pregnancy-related conditions) plus a symptom code. If it is simple myalgia with no pregnancy-specific cause, M79.18 is acceptable. Always code the pregnancy first (O00-O9A chapter).

8. Is there a code for bilateral buttock pain?

M79.18 does not distinguish between unilateral and bilateral. You can still use it for bilateral pain, but document “bilateral” clearly in your note. For bilateral myalgia of the buttocks, M79.18 is still correct.

Additional Resource: ICD-10 Coding Tool

For real-time code lookup and cross-referencing, bookmark this free resource from the AAPC (American Academy of Professional Coders):

AAPC ICD-10 Code Lookup Tool:
https://www.aapc.com/codes/icd-10

This tool allows you to search by keyword (e.g., “buttock pain”) and see all related codes, including exclusions and notes.

Final Thoughts for Medical Coders and Clinicians

The ICD-10 code M79.18 for unspecified buttock pain serves an important role. It allows you to accurately document a patient’s presentation when a specific etiology remains unclear after a reasonable evaluation.

However, treat M79.18 as a starting point, not an ending point. Use it for the first or second visit. Then, work toward a more specific diagnosis. Perform the appropriate exams. Consider imaging when warranted. Document your reasoning clearly.

By following the guidelines in this article, you will reduce denials, survive audits, and provide better care for your patients. That is a win for everyone.

Conclusion

The ICD-10 code for unspecified buttock pain is M79.18 (Myalgia, other site) . Use it only for muscle-type pain when more specific causes like sciatica, bursitis, or joint dysfunction have been reasonably excluded. Always document location, quality, duration, and your rule-out process to protect against denials and audits.

Disclaimer: This article is for educational purposes only and does not constitute legal, medical, or billing advice. ICD-10 codes and guidelines change annually. Always consult the latest official ICD-10-CM manual and payer-specific policies before submitting claims. The author and publisher disclaim any liability for any adverse outcomes resulting from the use or misuse of this information.