The 11 denial codes orthopedic billers see most, what each means in orthopedic terms, and when to correct versus appeal. With 2 copyable appeal letters.
| Code | What the payer is saying | What it usually means in orthopedics | The move |
|---|---|---|---|
| CO-16 | Claim lacks information or has submission errors | The catch-all: missing modifiers, invalid diagnosis pointers, incomplete patient data. In orthopedics this is frequently a laterality or modifier gap. | Fix the specific element named in the remark codes and resubmit; do not appeal a CO-16, correct it. |
| CO-18 | Duplicate claim | The claim was already received. Often triggered by resubmitting too fast rather than true duplication. | Check claim status before resubmitting; void and correct if the original was wrong. |
| CO-22 | Coordination of benefits: another payer is primary | Common with Medicare-age joint patients who also have employer coverage, and with work-related injuries. | Verify COB at scheduling, bill the correct primary, and rebill with the primary's EOB attached. |
| CO-29 | Timely filing limit expired | The claim arrived past the payer's deadline. In busy practices this is usually a workflow failure, not a billing one. | Appeal only with proof of timely original submission; otherwise this is a pure process loss. Track filing deadlines by payer. |
| CO-45 | Charge exceeds fee schedule (contractual adjustment) | Not an error: the difference between billed charges and the contracted rate. It becomes a problem only when posted incorrectly as patient responsibility. | No appeal; verify posting. If contracted rates look wrong, audit against the fee schedule in your contract. |
| CO-50 | Not medically necessary per the payer | The big orthopedic one: imaging before conservative therapy, injections beyond frequency limits, surgery without documented failed conservative care. | Appeal with the clinical record: conservative care timeline, exam findings, imaging results. Template below. |
| CO-97 | Bundled into another service (global period or NCCI edit) | Post-op visits billed inside a 90-day global, or procedures bundled by edit pairs. | Verify against global period rules; if the service was genuinely separate, appeal with modifier documentation (24, 25, 58, 59, 79 as applicable). |
| CO-151 | Frequency exceeds payer limits | Injection series and repeat imaging hit this: the payer's allowed count per timeframe was reached. | Verify the payer's frequency policy; appeal with documentation of medical necessity for the additional service. |
| CO-167 | Diagnosis not covered for this service | The ICD-10 code on the claim does not support the procedure under the payer's policy. | Check the payer's LCD/policy for covered diagnoses; correct coding if the record supports it, appeal with clinicals if policy is wrong for the case. |
| CO-197 | No prior authorization on file | The procedure needed precert and the claim shows none, or the auth number was omitted. | If auth exists, resubmit with the number. If not, request retro-authorization; template below. Prevention beats appeal here. |
| PR-204 | Service not covered under the patient's plan | A true benefits exclusion, landing as patient responsibility. | Verify benefits were checked pre-service; discuss options with the patient. Appeals rarely succeed on true exclusions. |
[Date] · [Payer appeals address] · Re: [Patient name, member ID, claim number, date of service]
To the Appeals Department: We are appealing the denial of [procedure, CPT code] for the above patient as not medically necessary. The clinical record, enclosed, documents: (1) [diagnosis with ICD-10] confirmed by [exam findings and imaging]; (2) a completed course of conservative management from [date] to [date] including [therapy, medications, injections] without adequate improvement; (3) functional impairment documented as [specifics]. The requested service meets the criteria in your medical policy [policy number, criteria section]. We request reversal of this denial and payment of the claim. Enclosed: clinical notes, imaging reports, therapy records, and the relevant policy excerpt.
Sincerely, [Physician name and credentials, NPI, practice contact]
[Date] · [Payer UM department] · Re: [Patient, member ID, date of service, procedure and CPT]
We are requesting retroactive authorization for the above service, performed on [date]. Authorization was not obtained in advance because [state the specific reason: urgent clinical circumstances, payer portal error with reference number, eligibility information available at the time]. The service met your plan's medical necessity criteria at the time of treatment, as documented in the enclosed record. We ask that authorization be granted retroactively and the associated claim [claim number] be reprocessed. Please contact [name, phone, fax] for any additional documentation.
Sincerely, [Physician name and credentials, NPI]
Almost every code in the table above traces to the front of the revenue cycle: eligibility not verified before the visit (CO-22, PR-204), authorization not confirmed before the procedure (CO-197), global-period rules not applied at scheduling (CO-97), frequency limits not checked before an injection series (CO-151). The appeal letter is the expensive version of a phone call that should have happened 2 weeks earlier.
That front-of-cycle work is exactly what ClinicFlow automates on every call: insurance captured and verified before the visit, visit types scheduled against global-period logic, and authorization-dependent procedures flagged into your prior auth workflow.
Claim adjustment reason codes: the standardized codes payers use on remittances to explain why a claim paid differently than billed. CO codes are contractual obligations, PR codes are patient responsibility.
Industry analyses consistently find that a majority of denials are avoidable and a large share of appealed denials are overturned. The bigger lesson is that most practices appeal too little because appeals take staff time they do not have.
Prevention at the front of the revenue cycle: eligibility checked before the visit, prior auth verified before the procedure, and global-period logic applied before billing post-op visits. Most orthopedic denials are front-desk and scheduling failures wearing billing clothes.
ClinicFlow's voice AI answers every call for orthopedic and surgical practices, 24/7. The demo line is the production agent.
