CPT® Code 27447

Last Updated: January 2026 | Verified for 2026 AMA, CPT & CMS Guidelines

Quick Reference: CPT 27447 (Total Knee Arthroplasty)

• Definition: Surgical replacement of the knee joint (distal femur condyles and proximal tibia plateau) involving both medial and lateral compartments, with or without resurfacing the patella (a “total” knee replacement).

• Global Period: 90 days. Routine post-op care is bundled. Work commonly performed as part of the arthroplasty (synovectomy, osteophyte removal, debridement, meniscectomy, lateral release, ligament/capsular balancing) is generally not separately reportable.

• Surgical Setting: Medicare removed TKA from the inpatient-only list in 2018 and added it to the ASC covered procedures list in 2020 for appropriately selected beneficiaries. Confirm payer rules for admission status and site-of-service.

• Bilateral Procedures: Same-session bilateral TKA is typically reported as 27447-50 or as payer-directed RT/LT line items. Many payers reimburse about 150% of the unilateral allowance for a bilateral primary TKA.

• Related Codes: 27446 partial/unicompartmental ; 27486 revision (one component) ; 27487 revision (femoral + tibial components) ; 27488 explant with/without spacer. Converting a partial knee to total knee has no dedicated “conversion” code; apply established guidance (see Scenario 3) and document component removal clearly.

CPT 27447 is the core code for a primary total knee arthroplasty (TKA). It describes replacement of the tibiofemoral joint surfaces in both compartments using prosthetic components, and it includes typical intra-operative steps needed to implant the prosthesis and restore alignment, stability, and motion. Because TKA is high volume and high cost, payer edits and audits are common; clean coding depends on accurate reading of the operative report, correct diagnosis selection, and appropriate modifier use.

Two patterns drive many denials. First, a procedure documented as unicompartmental arthroplasty is sometimes miscoded as 27447; payers expect 27446 when only one compartment is replaced. Second, coders sometimes “unbundle” routine knee work (meniscectomy, chondroplasty, synovial work) even though such services are typically included in the TKA package. The safest approach is to treat 27447 as the single comprehensive code for the operative event unless a truly separate service is performed. These principles reduce denials, speed payment, and support defensible orthopedic documentation.

Knee Arthroplasty Code Selection Decision Tree

flowchart TD
    A[Knee Arthroplasty<br/>Procedure] --> B{Primary or revision?}
    B -->|Primary| C{How many compartments<br/>replaced?}
    C -->|One - medial OR<br/>lateral only| D[CPT 27446<br/>Unicompartmental]
    C -->|Both medial AND lateral| E[CPT 27447<br/>Total Knee Arthroplasty]
    E --> F{Bilateral<br/>same session?}
    F -->|Yes| G[27447-50 or<br/>RT/LT per payer]
    F -->|No| H[Append RT or LT]
    B -->|Revision| I{Scope of revision?}
    I -->|One component| J[CPT 27486]
    I -->|Both femoral + tibial| K[CPT 27487]
    I -->|Explant with or<br/>without spacer| L[CPT 27488]
    I -->|Partial to total<br/>conversion| M[27487-52]
    E --> N{During global period<br/>of prior TKA?}
    N -->|Planned staged| O[Modifier -58]
    N -->|Unplanned complication| P[Modifier -78]
    N -->|Unrelated procedure| Q[Modifier -79]

    style E fill:#2563eb,color:#fff,stroke:#1e40af
    style D fill:#16a34a,color:#fff,stroke:#15803d
    style J fill:#f59e0b,color:#fff,stroke:#d97706
    style K fill:#f59e0b,color:#fff,stroke:#d97706

1. Procedure Description & CPT Code Details

Total knee arthroplasty replaces diseased articular surfaces of the distal femur and proximal tibia with prosthetic components (femoral component, tibial baseplate and insert, and optional patellar resurfacing). CPT 27447 signifies that both medial and lateral tibiofemoral compartments are addressed; patella resurfacing is optional within the same code descriptor.

Confirm “total” versus “partial.” Operative documentation should explicitly support a bicompartment tibiofemoral replacement. If the report describes only a medial or lateral compartment implant (unicondylar/partial), report 27446 rather than 27447. This distinction is clinically and financially significant and is a common target of payer review.

Included intra-operative work

Primary TKA requires exposure, bone preparation, balancing, and joint cleanup. Coding guidance commonly treats osteophyte removal, synovial debridement/partial synovectomy, meniscal debridement, patellar tracking maneuvers (including lateral release when performed to complete the arthroplasty), and routine ligament/capsular balancing as integral to the arthroplasty. These steps may be documented in detail, but they ordinarily do not create separately billable codes on the same knee and date.

Navigation and robotics

Use of computer navigation or robotics does not change the primary arthroplasty CPT. Practices sometimes report add-on navigation code 20985 or Category III navigation codes, but payer payment is inconsistent and many plans treat these services as inclusive or non-covered in TKA. If your payer allows the add-on, ensure documentation describes the navigation work performed and verify any required modifiers or claim notes.

2. Medical Necessity & Documentation Requirements

Medical necessity documentation is often the deciding factor in whether a TKA claim is paid, especially for commercial plans with prior authorization and for Medicare contractors conducting post-payment review. A Medicare contractor bulletin identifies insufficient documentation as a major denial reason for TKA and emphasizes that records must demonstrate why surgery was reasonable and necessary.

• Conservative treatment history: Document therapies tried (PT, medications, injections, bracing, activity modification) and response. Many payer criteria expect meaningful conservative treatment attempts before elective arthroplasty, unless contraindicated.

• Objective severity: Include imaging (X-ray/MRI reports) and correlate to exam findings (ROM limits, crepitus, effusion, deformity, instability). Commercial criteria commonly require imaging evidence of advanced disease plus functional impairment.

• Functional impact: Record ADL limitations (walking distance, stairs, sleep disruption, need for assistive device) and pain severity, ideally with time course and progression.

• Decision-making note: The preoperative assessment should document that risks, benefits, and alternatives were discussed and that arthroplasty was chosen after failed nonoperative care. If the decision for major surgery is made in an E/M visit immediately before surgery, modifier -57 may apply to that E/M per payer policy.

• Operative note clarity: Ensure laterality and total-compartment replacement are explicit; list components implanted and any unusual additional work if you anticipate modifier 22.

Documentation should be internally consistent: diagnosis laterality must match operative laterality, and the chart should support the etiology you code (primary OA versus inflammatory arthritis versus osteonecrosis). When a payer requests records, provide the consult note, imaging reports, and evidence of conservative therapy to align with typical coverage criteria.

3. Common ICD-10 Codes for TKA Indications

The procedure code remains 27447 across diagnoses, but ICD-10 coding supports coverage. Use the most specific, laterality-correct code that reflects the condition driving the replacement.

• M17.0, M17.11, M17.12: Primary knee osteoarthritis (bilateral, right, left). OA is the most common indication. For unilateral arthroplasty, use laterality-specific codes and avoid bilateral codes unless documentation supports bilateral disease in the clinical record.

• M17.4 and other secondary OA codes: Post-traumatic or secondary OA when prior injury or other cause is documented.

• M05.761/M05.762 and M06.861/M06.862: Rheumatoid arthritis affecting the knee, with laterality and serostatus distinctions. Ensure the chart documents inflammatory arthritis as the driver of joint destruction.

• Osteonecrosis/AVN codes: Use knee-appropriate osteonecrosis codes (e.g., M87 series when applicable) when imaging supports collapse or advanced structural compromise.

• Z96.651/Z96.652: Presence of artificial knee joint. These status codes are typically more relevant for follow-up or revision claims, but they can help contextualize revision services.

Many payers publish medical-necessity criteria that explicitly reference arthritis diagnoses, imaging severity, and functional limitation requirements. Accurate ICD-10 selection improves initial claim adjudication and strengthens appeals when denials occur.

4. Medicare & Payer Coverage Considerations

Setting rules affect admission status and patient cost-sharing, so they matter to surgeons and facilities even though the surgeon’s CPT remains 27447. CMS removed TKA from the inpatient-only list in 2018, permitting hospital inpatient or outpatient performance based on patient needs and documented expectation of care. CMS later added TKA to the ASC covered procedures list in 2020, allowing select low-risk beneficiaries to receive TKA in an ASC.

Commercial insurers generally cover primary TKA when criteria are met, but many require prior authorization. Policies typically require imaging evidence of advanced joint disease, functional impairment, and documented conservative therapy attempts. Medicare Advantage plans may require authorization for both the procedure and the admission type and may encourage outpatient pathways. For revision and infection cases, payers expect documentation of failure mode (loosening, instability, infection) and the clinical plan.

5. Modifier Usage (50, 58, 78, 79, 22, 54/55)

Modifiers are most critical when (1) both knees are treated, (2) a second procedure occurs within the global period, or (3) postoperative care is transferred. AAPC guidance on global surgical modifiers provides practical rules for choosing -58, -78, and -79 in orthopedic cases.

Modifier 50 (bilateral primary TKA)

For same-session bilateral TKAs, many payers accept a single line of 27447 with modifier 50; others require two lines with RT and LT. Follow payer instructions and ensure the op note clearly documents bilateral work. Bilateral reimbursement is commonly around 150% of the unilateral amount.

Modifiers 58, 78, 79 (subsequent procedures during the global)

-58 is for planned/staged or more extensive related procedures and generally restarts the global period from the later date. -78 is for an unplanned return to the operating room for a related complication; payment is commonly limited to the intraoperative portion and the original global period continues. -79 is for unrelated procedures during the global, including contralateral knee arthroplasty, and typically allows full payment and a new global period.

Modifier 22 (increased services)

Append -22 only when work is substantially greater than typical and your operative report explains the additional complexity (e.g., unusual deformity, major bone loss, or unusually prolonged operative time). Expect payer requests for op notes and variable additional payment.

Modifiers 54/55 (split global)

Use -54 for surgical care only and -55 for postoperative management only when care is formally transferred between providers, with the transfer documented. Orthopedic coding discussions of the TKA global package describe this split-billing approach when appropriate.

6. Global Period Rules & Bundled Services

With a 90-day global period, routine post-op visits and typical recovery management are bundled. The global package also includes many knee-related tasks that might be separately reportable in other contexts. Guidance describing knee replacement coding warns against billing additional knee procedures that are performed as part of achieving a stable, functional arthroplasty (for example meniscus debridement or synovial work). Separate billing is generally reserved for unrelated services or qualifying return-to-OR procedures.

Don’t “Unbundle” Routine Knee Procedures:

When coding 27447, do not add arthroscopy, meniscectomy, chondroplasty, or debridement codes solely because the op note mentions them. These steps are typically integral to the arthroplasty and are included in the surgical package.

7. Comparison of Related Knee Arthroplasty Codes

Conversion of a unicompartmental knee to a total knee is frequently coded using a revision framework (often 27487-52) rather than coding a primary TKA, consistent with published guidance discussed in coding resources.

8. Complex Clinical Scenarios & Examples

Scenario 1: Simultaneous Bilateral TKA in One Session

Patient: Severe bilateral knee OA. Both knees replaced during one anesthesia.

Coding: 27447-50 (or payer-required RT/LT reporting).

Rationale: -50 communicates bilaterality; reimbursement is commonly ~150% of unilateral and the global covers routine follow-up for both knees.

Scenario 2: Infected TKA – Two-Stage Revision

Patient: Deep periprosthetic infection identified within the global of a recent TKA.

Stage 1: Explant + spacer. Coding: 27488-78 (unplanned return to OR for related complication).

Stage 2: Reimplant after infection control. Coding: 27487-58 (staged, planned procedure).

Rationale: -78 does not restart global; -58 typically restarts global from the reimplant date.

Scenario 3: Conversion of Partial Knee to Total Knee

Patient: Prior unicompartmental implant with progression to multicompartment disease; surgeon removes the partial components and implants a total knee prosthesis.

Coding: 27487-52 is often recommended to reflect revision-like work with reduced scope relative to full TKA-to-TKA revision.

Rationale: No dedicated conversion code exists; clear op documentation of component removal and new implant placement is essential.

Scenario 4: Periprosthetic Femur Fracture ORIF During Global

Patient: Falls one month after TKA; distal femur fracture above the implant repaired with ORIF; implant retained.

Coding: Fracture fixation code (e.g., 27507) with modifier 78 for Medicare when treated as related return to OR in the operative region.

Rationale: -78 supports intraoperative payment while the original TKA global continues.

Across these examples, the operative note and postoperative timeline are the key billing “facts.” If the chart clearly states what was done, why it was necessary, and whether a later procedure was planned or complication-driven, correct coding usually follows directly.