Left Leg Pain ICD 10 Code: M79.605 Explained (FY 2027)

TL;DR

• The left leg pain ICD 10 code is M79.605 (Pain in left leg). It is billable and valid for FY 2027.
• Right leg pain uses M79.604. Unspecified leg pain uses M79.606.
• No single bilateral code exists. Report M79.604 and M79.605 together for pain in both legs.
• Use a site-specific code when the note names the thigh (M79.65-), lower leg (M79.66-), or foot (M79.67-).
• Once the provider confirms a cause such as sciatica, PAD, or DVT, code that condition instead.
• The most common denial trigger is M79.606 on imaging claims when laterality was already documented.

A patient walks in with left leg pain, and the claim goes out with a vague code. Weeks later, the payer denies the duplex study for missing laterality, and your team reworks the claim for pennies. This guide fixes that. It gives you the exact left leg pain ICD 10 code, M79.605, plus the right, bilateral, and unspecified codes, all checked against the FY 2027 ICD-10-CM code set effective October 1, 2026.

Leg Pain ICD 10 Codes at a Glance

Every general leg pain diagnosis code sits under subcategory M79.60, Pain in limb, unspecified. Coders choose the sixth character based on laterality, so the table below covers the four codes you will use most.

For bilateral leg pain, report M79.604 and M79.605 on the same claim. We explain why below.

All four codes live in Chapter 13, Diseases of the musculoskeletal system and connective tissue. You can verify each descriptor in the free CDC ICD-10-CM Browser Tool, which the National Center for Health Statistics updates every fiscal year.

M79.605 Pain in Left Leg: Full Code Details

M79.605 is a symptom code. Providers use it when a patient reports pain localized to the left lower limb and no confirmed diagnosis explains it yet. The pain can be acute or chronic, and it can span anywhere from hip to toes when the note does not narrow the site.

Where M79.605 sits in the code set

The code follows a clear path through the tabular list. Chapter 13 (M00-M99) leads to Other soft tissue disorders (M70-M79), then to category M79, subcategory M79.6 Pain in limb, hand, foot, fingers and toes, and finally to M79.60 Pain in limb, unspecified. The sixth character, 5, assigns the left leg.

Coding notes you must check

An Excludes2 note at M79.6 points joint pain to M25.5-. Therefore, if the provider documents left knee, hip, or ankle joint pain, you report M25.562, M25.552, or M25.572 instead. In addition, an Excludes1 note at M79 blocks psychogenic rheumatism (F45.8) and psychogenic soft tissue pain (F45.41) from being coded together with M79.605.

The code carries no code-first or use-additional-code instruction. As a result, you can report it alone or sequence it after a chronic pain code when the encounter calls for one.

Reference data for M79.605

• ICD-9-CM crosswalk: 729.5, Pain in limb
• MS-DRG grouping: 555 and 556, Signs and symptoms of musculoskeletal system and connective tissue
• Common synonyms: left leg pain, left lower extremity pain, LLE pain, pain in left lower limb

FY 2027 status

M79.605 remains valid for claims with dates of service from October 1, 2026 through September 30, 2027. The FY 2027 update made no descriptor or instructional note changes to the M79.6- subcategory. You can confirm this in the official CMS ICD-10-CM files, which include the annual addenda.

Right Leg Pain ICD 10 Code: M79.604

The right leg pain ICD 10 code is M79.604, Pain in right leg, with the inclusion term Pain in right lower limb NOS. It follows the same rules as M79.605, so the Excludes notes and reference data above apply equally.

Two common mistakes cost practices money here. First, M79.601 describes pain in the right arm, not the right leg. Second, M79.604 covers the entire right leg, not the right thigh, which has its own code at M79.651.

Finally, match laterality on both sides of the claim. When you pair M79.604 with a CPT code that takes an RT or LT modifier, the modifier must agree with the diagnosis. Payer edits catch this mismatch automatically, so check it before the claim leaves your system.

Bilateral Leg Pain ICD 10 Code: How to Code Both Legs

There is no bilateral option in the M79.60- subcategory. Therefore, the correct bilateral leg pain ICD 10 code is a pair: report M79.604 and M79.605 on the same claim.

The ICD-10-CM Official Guidelines for Coding and Reporting settle this. When a condition is bilateral and no bilateral code exists, you assign separate codes for the left and right sides. You can read the laterality rule in Section I.B.13 of the official guidelines published by CMS.

Many coders reach for M79.606 or M79.609 instead. However, both codes mean the side is unknown, not that both sides hurt. Payers read them as unspecified, and that reading drives denials.

Unspecified Leg Pain (M79.606): When It Works and When It Gets Denied

M79.606 is acceptable only when the entire record is silent on laterality. A telehealth triage note, an intake form completed before the exam, or a transferred chart with no side documented can all justify it.

On the other hand, if laterality appears anywhere in the encounter, you must use it. Check the history of present illness, the exam findings, and the imaging order. Coders who skip that check hand payers an easy reason to deny.

Medicare contractors and most commercial plans expect laterality on symptom codes. Consequently, M79.606 on a venous duplex, MRI, or physical therapy claim often returns a CO-11 diagnosis-to-procedure mismatch. When the note lacks a side, send a short query instead: “Please document laterality for the leg pain evaluated on [date].”

More Specific Codes: The Specificity Ladder

Code to the most specific site the provider documents. If the note says calf, shin, thigh, foot, or toes, drop M79.605 and climb to the site code. Joint pain moves to M25.5- because of the Excludes2 note.

For example, “left calf pain after running” codes to M79.662, not M79.605. Likewise, “left knee pain with effusion” belongs in M25.562. Each step down the ladder tells the payer exactly what the provider examined.

When Not to Use M79.605: Code the Cause Instead

Symptom codes give way to a confirmed diagnosis. The official guidelines state that signs and symptoms integral to a definitive diagnosis are not reported separately. So once the provider names the cause, you code that condition and drop M79.605 unless the pain is not routinely associated with it.

Suspected conditions are different. In the outpatient setting, you never code “rule out DVT” as DVT. Instead, you report M79.605 or M79.662 for the pain until the duplex confirms the clot. The same rule applies to suspected sciatica: report the limb pain code until the provider documents radicular pain.

Chronic Left Leg Pain and Pain Management Visits

Chronic pain adds one more code. When the provider documents chronic left leg pain and the visit is for pain management, sequence G89.29, Other chronic pain, first and follow it with M79.605 to identify the site.

The provider must write the word “chronic” for G89.29 to apply. Moreover, if the visit treats the underlying condition rather than the pain itself, leave G89.29 off the claim.

Coding Leg Pain With Other Symptoms

Patients rarely report pain alone. Report each documented symptom that the provider evaluates, and sequence the chief complaint first.

• Pain with swelling: M79.605 plus R60.0, Localized edema
• Pain with numbness or tingling: M79.605 plus R20.0 or R20.2
• Pain with weakness: M79.605 plus M62.81, Muscle weakness, generalized
• Pain with cramping: M79.605 plus R25.2, Cramp and spasm

Documentation Checklist for Left Leg Pain Claims

Clean documentation makes every code choice above automatic. Ask providers to capture these elements in each note:

• Laterality (left, right, or both)
• Anatomical site (thigh, calf, shin, foot, or joint)
• Onset and duration, including the word “chronic” when it applies
• Character of the pain (aching, burning, sharp, radiating)
• Aggravating and relieving factors
• Associated symptoms such as swelling, numbness, or weakness
• Suspected versus confirmed cause
• Orders linked to the diagnosis

Compare two notes for the same visit. The weak note reads: “Leg pain, order venous duplex.” That note forces M79.606 and invites a denial. The strong note reads: “Left calf pain for five days, worse with walking, tender left gastrocnemius, no swelling. Rule out DVT; order left lower extremity venous duplex.” That note supports M79.662 with the LT modifier and passes the first time.

Common Denial Reasons and How to Fix Them

Most leg pain denials trace back to five errors. Fix them at the front end, and your rework queue shrinks fast.

Run a quick audit of your last 30 denied leg pain claims. In most practices, the unspecified code and the laterality conflict account for the majority, and both are fixable at the coding desk.

CPT Codes Commonly Billed With M79.605

M79.605 supports the diagnostic work-up for left leg pain. It pairs most often with:

• Office visits: 99202 to 99215
• Venous duplex: 93970 (bilateral) or 93971 (unilateral)
• Arterial duplex: 93925 (bilateral) or 93926 (unilateral)
• Tibia and fibula X-ray: 73590 or 73592
• Physical therapy evaluation: 97161 to 97163

Keep one rule in mind. A symptom code justifies the tests that search for a cause, but ongoing therapy usually needs a definitive diagnosis to satisfy payer policy.

What M79.605 Means on a Patient Bill

If you found M79.605 on an explanation of benefits, it simply means your provider recorded pain in your left leg without naming a cause yet. It is a symptom code, not a disease diagnosis. After tests come back, the code on later claims may change to reflect what your provider found.

Conclusion

Code left leg pain to M79.605, right leg pain to M79.604, and bilateral pain to both. Climb to a site code when the note names the thigh, calf, or foot, and switch to the cause code once the provider confirms a diagnosis. Above all, capture laterality every time. That single habit prevents most leg pain denials before they start.

Related Guides and Resources

• Right Hip Pain ICD 10 Code: M25.551 Explained
• Right Shoulder Pain ICD 10 Code: M25.511 Coding Guide 2026-2027
• Anemia ICD-10 Codes: A Complete Guide for Coders & Providers 2026-2027
• 99203 CPT Code: Complete Billing, Time & Reimbursement Guide 2026
• 99205 CPT Code: Description, Time, MDM and Billing Guide 2026-2027
• CBC CPT Code: 85025 vs. 85027 & Billing Guidelines 2026
• CPT Code 80061: Complete Lipid Panel Billing Guide 2026
• CPT Code for Renal Ultrasound: 76770 vs 76775 Guide 2026

Official Sources

• CMS: ICD-10-CM Files and Official Guidelines for Coding and Reporting, FY 2027
• CDC National Center for Health Statistics: ICD-10-CM Browser Tool
• CDC NCHS: ICD-10-CM Official Guidelines

Frequently Asked Questions

What is the ICD-10 code for left leg pain? 

The ICD-10-CM code for left leg pain is M79.605, Pain in left leg. Use it when the provider documents pain in the left lower limb without a confirmed cause.

Is M79.605 a billable code? 

Yes. M79.605 is a complete six-character code, so payers accept it on HIPAA claims. It is valid for the FY 2027 code set through September 30, 2027.

What is the ICD-10 code for right leg pain? 

Right leg pain codes to M79.604, Pain in right leg. Do not confuse it with M79.601, which describes right arm pain.

What is the ICD-10 code for bilateral leg pain? 

No bilateral code exists. Report M79.604 and M79.605 together. For both lower legs, report M79.661 and M79.662.

When should I use M79.606 instead of M79.605? 

Use M79.606 only when nothing in the record identifies the side. If laterality appears anywhere in the encounter, code it.

What is the difference between M79.605 and M79.662? 

M79.605 covers the whole left leg. M79.662 narrows the pain to the left lower leg, meaning the calf or shin. Choose M79.662 when the note names that site.

Can M79.605 be the primary diagnosis? 

Yes. When leg pain is the reason for the visit and no definitive diagnosis exists, M79.605 can be the first-listed code.

How do I code chronic left leg pain? 

For a pain management encounter, sequence G89.29 first, then M79.605. The provider must document the pain as chronic.

Did M79.605 change in the FY 2027 ICD-10-CM update? 

No. The FY 2027 update effective October 1, 2026 left M79.605 and the rest of the M79.6- subcategory unchanged.