MRI Knee CPT Codes (73221-73223)

Knee MRI is one of the highest-volume advanced imaging services in orthopedic and radiology billing, and three distinct CPT codes govern contrast protocol selection. Misidentifying which protocol was performed, bundling two codes for the same joint on the same date, or applying modifier 50 to a bilateral indicator 3 code are active RAC audit targets that generate significant recoupments. CPT codes 73721, 73722, and 73723 each correspond to a specific gadolinium protocol for lower extremity joint MRI; this guide covers protocol-driven code selection, bilateral billing mechanics, MR arthrography coding, NCCI bundling rules, and documentation requirements.

What the Procedure Involves

Knee MRI uses magnetic resonance technology to image intra-articular and periarticular structures, including the menisci, cruciate and collateral ligaments, articular cartilage, synovium, subchondral bone, and periarticular soft tissues. The radiologist acquires multiple pulse sequences in different imaging planes; whether gadolinium contrast is administered, and at what point in the acquisition sequence, directly determines which CPT code applies. A non-contrast examination (73721) consists solely of pre-contrast sequences with no gadolinium administration. A with-contrast-only examination (73722) administers IV gadolinium without acquiring pre-contrast sequences, a less common protocol reserved for cases where baseline sequences add no diagnostic value. The without-and-with protocol (73723) acquires pre-contrast sequences, administers IV gadolinium, then acquires additional post-contrast sequences in the same session, providing the highest diagnostic yield for tumor evaluation, avascular necrosis, inflammatory arthritis, and post-operative assessment.

MR arthrography, where gadolinium is injected directly into the joint space rather than administered intravenously, is a distinct technique coded separately: CPT 27369 covers the injection procedure, paired with 73722 or 73723 based on whether additional IV gadolinium sequences were also acquired. Confirming the contrast protocol from the radiology report technique description is the single most critical step in selecting among these three codes.

Quick Reference: CPT Codes

Common ICD-10-CM Diagnoses

Code Selection Decision Logic

The correct code follows directly from the radiology report technique description. Read the technique section first; do not rely solely on the order or the requisition, since what was ordered and what was performed may differ.

graph TD
    A[Knee MRI Ordered] --> B{Intra-articular injection\nperformed before imaging?}
    B -->|Yes - Direct Arthrogram| C[Report 27369 for injection\nAdd 77002 if fluoroscopic guidance documented]
    C --> D{Additional IV gadolinium\nalso administered?}
    D -->|No| E[[73722](https://www.codingahead.com/cpt/codes/73722)]
    D -->|Yes| F[[73723](https://www.codingahead.com/cpt/codes/73723)]
    B -->|No - Standard MRI| G{IV Gadolinium\nadministered?}
    G -->|No| H[[73721](https://www.codingahead.com/cpt/codes/73721)]
    G -->|Yes| I{Pre-contrast sequences\nalso acquired?}
    I -->|No| J[[73722](https://www.codingahead.com/cpt/codes/73722)]
    I -->|Yes| K[[73723](https://www.codingahead.com/cpt/codes/73723)]

The critical audit point: when both pre- and post-contrast sequences appear in the technique description, only 73723 is reportable. Billing 73721 and 73723 together for the same knee on the same date is the most common bundling violation for these codes and an active RAC audit topic (RAC 0147).

Code-by-Code Breakdown

CPT 73721 — MRI, Joint of Lower Extremity; Without Contrast

Official descriptor: "Magnetic resonance (eg, proton) imaging, any joint of lower extremity; without contrast material"

Procedure match: Non-contrast knee MRI is appropriate for the majority of musculoskeletal indications, including meniscal tears, ligament injuries (ACL, PCL, MCL, LCL), articular cartilage evaluation, osteochondritis dissecans, stress fractures, and pre-surgical osteoarthritis staging. Gadolinium does not improve diagnostic yield for these indications and adds cost and patient risk.

Common confusion: Do not use 73721 when direct intra-articular contrast was injected for arthrography. Intra-articular gadolinium constitutes "contrast material"; the code becomes 73722, not 73721, even if no IV gadolinium was administered. Also avoid confusing 73721 with 73718, which covers MRI of lower extremity soft tissue or bone not coded to a specific joint.

Documentation requirements: Technique description confirming no gadolinium administration; clinical indication supporting medical necessity; ordering physician's signed order.

Modifier considerations: Modifier 26 for radiologist interpretation in a hospital or IDTF setting; modifier TC for facility or IDTF equipment and staff. RT or LT required for laterality; auditors look for laterality modifiers on all extremity imaging claims. MUE is 3 units per date of service; bilateral billing = 1 unit per side on separate claim lines.

CPT 73722 — MRI, Joint of Lower Extremity; With Contrast

Official descriptor: "Magnetic resonance (eg, proton) imaging, any joint of lower extremity; with contrast material(s)"

Procedure match: 73722 applies when IV gadolinium is administered and no pre-contrast sequences were acquired. It also applies to MR arthrography when direct intra-articular gadolinium is injected and no additional IV contrast sequences follow. This is the less common protocol in most practices; most "with contrast" protocols acquire baseline pre-contrast sequences, making 73723 the more frequent choice.

Common confusion: If the radiology report shows any pre-contrast sequences before gadolinium administration, the correct code is 73723, not 73722. Billing 73722 when 73723 was performed undercodes the service and creates a documentation mismatch that surfaces on post-payment audit. The compliance distinction here is what sequences appear before gadolinium in the technique section.

Documentation requirements: Technique description confirming gadolinium administration without prior sequences; if MR arthrography, documentation of intra-articular injection (report separately with 27369); clinical indication supporting contrast use. TC RVUs include the cost of paramagnetic contrast media; do not separately bill a HCPCS code for gadolinium. MUE is 2 units per date.

CPT 73723 — MRI, Joint of Lower Extremity; Without Contrast Followed by Contrast and Further Sequences

Official descriptor: "Magnetic resonance (eg, proton) imaging, any joint of lower extremity; without contrast material(s), followed by contrast material(s) and further sequences"

Procedure match: 73723 is the most comprehensive code and applies when the radiologist acquires pre-contrast sequences, administers IV gadolinium, and then acquires additional post-contrast sequences in the same session. This protocol is standard for tumor evaluation, avascular necrosis, post-operative assessment, infection workup, and inflammatory arthritis where enhancement patterns are diagnostically critical.

Common confusion: When 73723 is performed, do not also bill 73721 for the pre-contrast component. The combined study is one service coded to one code; splitting it into 73721 + 73722 or reporting 73721 + 73723 on the same knee on the same date is the classic RAC 0147 bundling violation. Auditors look for same-day, same-joint claims carrying more than one of these three codes.

Documentation requirements: Technique description explicitly documenting pre-contrast sequences, gadolinium administration, and post-contrast sequences; clinical justification for contrast use; signed written report. TC RVUs include gadolinium cost. MUE is 2 units per date.

Bundling, Unbundling & NCCI Edits

RAC Topic 0147 — MRI Bundling (active): When a more comprehensive MRI of the same anatomic site is performed on the same date, the less comprehensive code is denied. The bundling hierarchy is:

• 73721 + 73723 for the same knee, same date: 73721 denied
• 73722 + 73723 for the same knee, same date: 73722 denied
• 73721 + 73722 for the same knee, same date: 73721 denied

Only the single most comprehensive code reflecting the actual study performed should be billed. No modifier overrides this denial. CMS RAC Topic 0147

NCCI PTP edits: The NCCI Policy Manual Chapter 9 (Radiology, CPT 70000-79999, updated 1/1/2026) governs all procedure-to-procedure edit pairs within the radiology section. Review PTP edit tables for any additional column 1/column 2 pairs when billing 73721-73723 alongside other radiology codes on the same date.

MR arthrography: 27369 is correctly reported alongside 73722 or 73723 for MR arthrography; it is not a standalone code without the associated imaging service. CPT 27370 was deleted January 1, 2019 and replaced by 27369; claims submitted with 27370 are denied. 20610 (arthrocentesis, major joint) may be reported for a separate, distinct aspiration or injection procedure; it is not a substitute for 27369 when contrast arthrography is performed.

Inpatient TC bundling (RAC Topic 0062): The technical component of 73721-73723 is bundled into Medicare Part A payment during an inpatient admission. Radiologists may bill the professional component (modifier 26) for their interpretation, but billing TC during an inpatient stay triggers automatic denial and RAC recoupment. CMS RAC Topic 0062

MPPR: All three codes carry Multiple Procedures indicator 4. When the same provider bills multiple diagnostic imaging services in the same imaging family on the same date, the TC of the subsequent service is reduced by 50%. The professional component (modifier 26) is not subject to MPPR.

Medicare & Payer Rules

CMS NCD 220.2: All Medicare knee MRI coverage is governed nationally by NCD 220.2. Coverage requires the study to be reasonable and necessary for the individual patient's condition; NCD 220.2 does not enumerate a specific covered diagnosis list. MRI equipment must have FDA premarket approval and be operated within FDA-approved parameters. Coverage is limited where cardiac pacemakers (unless MR-conditional per FDA protocol) or certain metallic implants are present.

MAC LCDs: No national LCD exists specifically for 73721-73723. Individual Medicare Administrative Contractors issue jurisdiction-specific LCDs with ICD-10-CM covered diagnosis code lists that vary by jurisdiction. Check the CMS Medicare Coverage Database for your MAC's active LCD.

AUC Program: CMS paused AUC enforcement effective January 1, 2024 (CY 2024 PFS Final Rule). As of 2026, providers are not required to attach AUC consultation information to Medicare FFS claims for advanced diagnostic imaging, including 73721-73723. CMS AUC Program

Contrast billing: TC RVUs for 73722 and 73723 include paramagnetic contrast media cost per the CMS Claims Processing Manual, Chapter 13. CMS does not make additional payment for three or more MRI sequences in a single session; payment reflects two sequences regardless of additional sequences acquired. Do not separately bill a HCPCS code for gadolinium alongside the TC of these codes.

Medicare Advantage prior authorization: MA plans may impose prior authorization for knee MRI. The CY 2025 MA Final Rule (CMS-4205-F) restricts MA plans from creating PA barriers beyond Traditional Medicare standards. The CMS Interoperability and Prior Authorization Final Rule (CMS-0057-F), effective January 1, 2026, requires impacted MA payers to process standard PA requests within 7 calendar days and expedited requests within 72 hours.

PC/TC indicator = 1: 73721-73723 are split-billable services. When a radiologist works in a hospital or IDTF, bill the professional component with modifier 26; the facility bills TC. When the physician owns the equipment and performs the service in their own office, bill the global code with no modifier.

Frequency: NCD 220.2 imposes no hard frequency limit. MAC LCDs may specify episode-of-care based frequency parameters. Repeat MRI of the same knee within a short interval requires documented clinical change or new indication; lack of supporting documentation is a recurring audit finding.

Documentation Checklist

1. Written, signed order from the treating or ordering physician on file before the study is performed, including the clinical indication or diagnosis
2. Documentation establishing the study is reasonable and necessary for this specific patient (ordering note, referral, or clinical summary supporting the indication)
3. Radiology report technique section explicitly confirming: whether gadolinium was administered (none, IV only, intra-articular, or both); timing of contrast relative to sequences (pre-contrast only, post-contrast only, or without/then/with)
4. Complete radiology report: pertinent clinical history, comparison to prior studies when available, technique, findings by anatomic structure, and impression
5. Signed written interpretation by the interpreting physician; verbal or phone-only interpretations do not satisfy billing requirements
6. Laterality documentation for each knee if bilateral; each side requires independent medical necessity documentation
7. If MR arthrography (27369): documentation of injection procedure, contrast type used, guidance method (fluoroscopic per 77002 if applicable), and performing provider credentials
8. Contrast justification when billing 73722 or 73723: documentation reflecting the clinical reason contrast was indicated, not merely "ordered with contrast"
9. Patient status confirmed before billing TC; do not bill TC during inpatient admission

Common Billing Errors & Denial Prevention

1. Using 73221-73223 for knee MRI. Codes 73221, 73222, and 73223 are for upper extremity joint MRI (shoulder, elbow, wrist). Knee MRI is lower extremity and requires 73721-73723. This error may not trigger an automatic rejection at all payers, but the mismatch between diagnosis and code surfaces on audit.

2. Billing 73721 and 73723 for the same knee on the same date (RAC 0147). Both pre- and post-contrast sequences in a single session equal one service: 73723. Reporting them as two codes is a bundling violation; 73721 is denied with no modifier override. Bill only 73723.

3. Applying modifier 50 to bilateral knee MRI (RAC 0164). Codes 73721-73723 carry bilateral indicator 3; the standard 150% bilateral payment adjustment does not apply. Bilateral billing requires RT and LT modifiers on separate claim lines at 100% of the fee schedule each. Modifier 50 on these codes is an active RAC audit topic. RAC Topic 0164

4. Separately billing gadolinium contrast. TC RVUs for 73722 and 73723 include paramagnetic contrast media. Adding a separate HCPCS line for gadolinium is incorrect and will be denied or recouped.

5. Billing 73722 when 73723 was performed. If the radiology report technique section shows any pre-contrast sequences before gadolinium administration, the correct code is 73723. Billing 73722 undercodes the service and creates a documentation mismatch; auditors compare the claim code against the report technique description.

6. Missing physician order or unsigned radiology report. OIG audit findings (OEI-07-09-00450) identified missing physician orders in 12% of CT/MRI claims and missing supporting interpretation documentation in another 12%. Both are automatic denial or recoupment triggers on audit.

7. TC billing during inpatient admission. TC is bundled into Medicare Part A payment; billing 73721-TC, 73722-TC, or 73723-TC during an inpatient stay triggers automatic denial. Radiologists should bill the professional component (modifier 26) only for hospital inpatient reads.

8. Using deleted code 27370 for MR arthrography injection. CPT 27370 was deleted January 1, 2019 and replaced by 27369. Claims submitted with 27370 are denied; update charge masters accordingly.

Clinical Scenario Examples

Scenario 1: Meniscal tear workup, right knee A 42-year-old presents with right knee pain and mechanical clicking after a twisting injury; plain films are negative. The orthopedist orders MRI right knee without contrast. The radiology report technique confirms no gadolinium administration.

• Codes: 73721-RT (global); 73721-26-RT (radiologist in hospital); 73721-TC-RT (facility)
• ICD-10-CM: M23.200
• Rationale: No contrast administered; laterality modifier RT required on all claim lines

Scenario 2: Bilateral pre-surgical osteoarthritis evaluation A 68-year-old with bilateral knee pain requires MRI for pre-surgical planning. The surgeon orders bilateral knee MRI without contrast.

• Codes: 73721-RT (line 1) and 73721-LT (line 2); do NOT use modifier 50
• ICD-10-CM: M17.11 for right knee, M17.12 for left knee
• Rationale: Bilateral indicator 3 requires RT and LT on separate lines at 100% each. MPPR reduces TC of the second study by 50%. Each side requires independent medical necessity documentation.

Scenario 3: MR arthrography for suspected chondral defect, left knee A 35-year-old athlete with recurrent knee effusion and suspected osteochondral lesion. Sports medicine orders MR arthrography left knee. Fluoroscopic guidance is used for intra-articular injection; no additional IV gadolinium is administered.

• Codes: 27369-LT + 73722-LT + 77002
• ICD-10-CM: M94.261 or applicable chondral defect code for left knee
• Rationale: 27369 for the injection procedure, 73722 because intra-articular contrast was administered without additional IV sequences, 77002 for documented fluoroscopic guidance

Scenario 4: Tumor protocol, left knee A 55-year-old presents with an incidental soft tissue mass adjacent to the left knee. The radiologist acquires pre-contrast sequences, administers IV gadolinium, then acquires post-contrast sequences in the same session.

• Code: 73723-LT
• ICD-10-CM: D48.1 or C40.20 if malignant
• Rationale: Pre-contrast and post-contrast sequences in the same session = 73723. Splitting into 73721 + 73722 is RAC 0147 bundling violation.

Scenario 5: Inpatient knee MRI during Medicare admission A Medicare patient admitted for hip surgery develops a knee complaint. Radiology performs knee MRI in the hospital MRI suite during the inpatient stay.

• Code for radiologist: 73721-26-RT (or applicable contrast code with modifier 26 only)
• TC: Do NOT bill; bundled into Medicare Part A inpatient payment (RAC 0062)
• Rationale: The facility TC is covered under the inpatient DRG; the radiologist interprets and bills professional component only.

Related Procedures & Cross-References

Sources

• CMS NCD 220.2 — Magnetic Resonance Imaging — National coverage policy governing Medicare MRI
• CMS Claims Processing Manual, Chapter 13 (Radiology) — Billing rules for radiology services including PC/TC, contrast, and sequence payment
• CMS NCCI Policy Manual 2026, Chapter 9 (Radiology) — Bundling rules for CPT 70000-79999, effective 1/1/2026
• CMS NCCI PTP Edit Tables — Downloadable procedure-to-procedure edit files
• CMS NCCI MUE Tables — Per-day unit limits by CPT code (quarterly updates)
• CMS RAC Topic 0147 — MRI Bundling — Active RAC audit: less extensive MRI bundled into more extensive on same date
• CMS RAC Topic 0164 — Bilateral Indicator 3 Incorrect Coding — Active RAC audit: modifier 50 incorrectly applied to bilateral indicator 3 codes
• CMS RAC Topic 0062 — TC of Radiology Inpatient — TC bundled into Medicare Part A during inpatient admissions
• CMS Appropriate Use Criteria Program — AUC enforcement paused January 1, 2024
• CMS Prior Authorization Final Rule CMS-0057-F — Electronic PA requirements for MA plans, effective January 1, 2026
• CMS CY 2025 MA Final Rule CMS-4205-F — MA prior authorization requirements
• CMS CY 2026 PFS Final Rule Fact Sheet — 2026 conversion factors and payment policies
• CMS Medicare Coverage Database Search — MAC-specific LCD search by CPT code
• HHS OIG Report OEI-07-09-00450 — Radiology in Emergency Departments — Documentation audit findings for CT/MRI claims
• ACR Appropriateness Criteria — Clinical decision support for imaging selection by indication; MSK panels updated 2024-2025