78 used for a planned, staged procedure (58) or an unrelated one (79).
Why it matters in orthopedics
Orthopedic claims count units constantly: joints injected or aspirated, implants removed, fractured bones treated, drug units given with an injection. An MUE denial is a coding denial, not a medical-necessity denial, so the denied units can’t be billed to a Medicare patient, even with an Advance Beneficiary Notice.
How it works
Each value reflects the most units reported on the vast majority of correctly coded claims. CMS publishes separate MUE tables for practitioner services, outpatient hospital services and DME suppliers, and updates them quarterly on the same schedule as PTP edits. Each code’s MUE Adjudication Indicator (MAI) sets how the limit is applied:
MAI | How the edit works |
|---|---|
1 | Claim line edit; a line over the value is denied in full. Correctly reported extra units may go on separate lines with modifiers such as 59, XE, XS, XP, XU, 76, 77, 91 or anatomic modifiers, and each line is checked on its own |
2 | Date-of-service edit based on policy; units on all lines are summed. More units would contradict statute, regulation or coding policy, so contractors won’t override it in processing, reopening or redetermination |
3 | Date-of-service edit based on clinical benchmarks; units on all lines are summed. If records show the extra units were provided, correctly coded and medically necessary, the contractor may pay them |
CMS publishes most MUE values, but some are confidential, and not every code has an MUE. MUEs aren’t utilization targets: claims under the limit can still be reviewed, and a MAC may apply a stricter units edit.
For bilateral surgery, Medicare practitioners and outpatient hospitals report one line with modifier 50 and one unit unless the code itself is defined as bilateral, and MUE values for those codes assume that reporting. Ambulatory surgery centers report RT and LT on two lines instead.
Orthopedic example
Joint injections: for arthrocentesis and injection codes 20600–20611, one unit is a joint plus its surrounding bursae. Injecting a shoulder joint and two of its bursae without ultrasound is one unit of 20610 (major-joint aspiration or injection without ultrasound guidance). In CMS’s 2026 fee schedule data, 20610 has a bilateral surgery indicator of 1, so a bilateral knee injection on a Medicare practitioner claim goes on one line with modifier 50 and one unit.
Implant removal: 20670 and 20680 (superficial or deep implant removal) allow one unit per anatomic site, however many screws, plates or wires come out.
Fractures: closed treatment without manipulation of several metacarpals in one hand is one unit of 26600 per hand.
Digits: finger and toe procedures use FA, F1–F9 and TA, T1–T9 modifiers, and many have an MUE of 1 because each digit goes on its own modified line.
Drugs: J-code MUEs are based on prescribing information, how the product is supplied and claims data, so convert the dose given into the units the HCPCS code describes.
Common denial triggers
Units on one line above the MUE (MAI 1) with no supported separate-line modifier.
Units summed across lines above the value (MAI 2 or 3).
A bilateral procedure reported as two units instead of modifier 50 with one unit.
Drug units calculated from the dose given rather than the HCPCS unit.
How to prevent or fix
Check the current quarter’s practitioner MUE table and MAI before submitting multi-unit lines.
Split lines with anatomic, 59 or X modifiers only when the record supports separate sites or encounters.
Appeal MAI 3 denials with records showing the units were furnished and necessary; MAI 2 limits won’t be overridden.
Ask CMS in writing to reconsider a value you believe is wrong, and suggest an alternative value.
Treat frequent bypassing as a warning sign; CMS says it may mean units are being counted incorrectly. For other denial patterns, see common orthopedic claim denials.
Frequently asked questions
Can an ABN make the patient responsible for MUE-denied units?
No. CMS treats MUE denials as coding denials rather than medical-necessity denials, so an Advance Beneficiary Notice doesn’t shift liability, and the provider can’t bill the Medicare patient for units denied by an MUE. The provider can appeal, and for codes with an MAI of 3 the contractor may pay extra units that the medical records support.
Why can’t we find an MUE value for a code?
Not every code has an MUE, and CMS keeps some values confidential. Confidential MUE values aren’t published and may not be shared by anyone who obtains them. Check the current quarter’s practitioner, outpatient hospital or DME supplier table on the CMS MUE page before assuming a code has no limit.
Should we bill up to the MUE value?
No. MUEs aren’t utilization guidelines. The usual number of units for many codes is lower than the MUE value, and claims under the limit can still be reviewed by claims contractors, auditors and the Department of Justice. Report only the units that were actually furnished, counted correctly and medically necessary.
Guides that cover this term
Sources
Medicare NCCI Medically Unlikely Edits (MUEs) — CMS, last modified August 31, 2026
Chapter 1 - General Correct Coding Policies — CMS Medicare NCCI Policy Manual (Section V, Medically Unlikely Edits), revision date January 1, 2026
Chapter 4 - Surgery: Musculoskeletal System CPT Codes 20000-29999 — CMS Medicare NCCI Policy Manual (Section H, MUEs), revision date January 1, 2026
Introduction for National Correct Coding Initiative Policy Manual for Medicare Services — CMS, revision date January 1, 2026
Indicators for 2026 — CMS Medicare Physician Fee Schedule data, modified October 1, 2026
This entry is educational and is not legal, coding-compliance or billing advice. Payer rules change often, so confirm requirements with the payer before you bill. CPT® is a registered trademark of the American Medical Association; code descriptions here are Rette’s plain-language summaries.