CPT 73721 reports a magnetic resonance imaging (MRI) study of any joint of the lower extremity, such as the hip, knee or ankle, performed without contrast material.
It is one of the most frequently billed advanced imaging codes in orthopedic, sports medicine and radiology practices, because a non-contrast knee MRI is the standard study for suspected meniscus and ligament injuries. That volume also makes it a frequent target for prior authorization requirements and claim edits.
Most 73721 problems come from picking the wrong code family (joint versus other than joint), the wrong contrast code, a missing laterality or component modifier, or an authorization that does not match the study that was actually performed.
This guide covers the full 73718 to 73723 family, when to use RT, LT, 26 and TC, the 2026 Medicare national payment for each component, the multiple procedure payment reduction, and how radiology benefit managers review these requests.
Key Takeaways
- 73721 is MRI of any lower extremity joint without contrast. 73722 is with contrast and 73723 is without contrast followed by contrast.
- 73718 to 73720 are for the lower extremity other than a joint, such as the thigh or calf, not for a single joint.
- Bill the global code when you own the scanner and read the study, 73721-26 for the interpretation only, and 73721-TC for the technical component only.
- Using the 2026 conversion factor of $33.4009, the national Medicare amount is about $204.41 globally: $62.79 for the professional component and $141.62 for the technical component, before geographic adjustment.
- Original Medicare does not require prior authorization for a lower extremity MRI, but most Medicare Advantage, Medicaid managed care and commercial plans do, often through a radiology benefit manager.
CPT 73721 Description and the Lower Extremity MRI Code Family
The lower extremity MRI codes split on two questions: is the area imaged a joint, and was contrast used? Choosing the right row is the first step to a clean claim. For a refresher on how CPT codes are structured, see our guide to CPT, ICD-10 and HCPCS codes.
| CPT code | Area | Contrast | Typical use |
|---|---|---|---|
| 73718 | Lower extremity, other than joint | Without | Thigh or calf muscle, soft tissue mass, stress injury of the shaft |
| 73719 | Lower extremity, other than joint | With | Soft tissue mass or infection where contrast is needed |
| 73720 | Lower extremity, other than joint | Without, then with | Mass characterization, osteomyelitis work-up |
| 73721 | Any joint of lower extremity | Without | Knee internal derangement, ankle ligament injury, hip pain |
| 73722 | Any joint of lower extremity | With | Often used for MR arthrography after an intra-articular injection |
| 73723 | Any joint of lower extremity | Without, then with | Inflammatory arthritis, infection, post-operative joint |
Coding rule of thumb. Code the anatomy that was imaged and the contrast that was actually given. The order says what was requested; the radiology report says what was done, and the report drives the code.
When both hips are imaged together in one field of view, some payers expect a pelvis MRI code (72195 to 72197) rather than two units of 73721. Check the payer’s radiology policy before you bill bilateral hip studies.
73721 vs 73722 vs 73723: Picking the Contrast Code
Contrast status is the most common source of a mismatch between the authorization and the claim. If a plan approved 73721 but the radiologist added a post-contrast sequence, the study became 73723, and the authorization usually needs to be updated.
| Scenario | Correct code | Why |
|---|---|---|
| Knee MRI, no contrast | 73721 | Joint study, no contrast at any point |
| Knee MR arthrogram | 73722 plus the injection code | Contrast placed in the joint; the injection is reported separately (27369 for the knee) |
| Ankle MRI, pre and post IV contrast | 73723 | Both non-contrast and contrast sequences in one session |
| Calf mass, no contrast | 73718 | Not a joint, so the other-than-joint family applies |
For hip and ankle arthrography, the injection is reported with 27093 (hip) or 27648 (ankle). In office and imaging center settings, the gadolinium contrast agent itself may be billed with a HCPCS A-code when the payer allows it.
Modifiers for CPT 73721: RT, LT, 26 and TC
| Modifier | Meaning | When to use |
|---|---|---|
| RT / LT | Right side / left side | Identify which limb was imaged; many payers edit for missing laterality on extremity imaging |
| 26 | Professional component | The radiologist reads the study but does not own the equipment, for example in a hospital |
| TC | Technical component | The facility or imaging center performs the scan but another provider bills the read |
| No modifier | Global service | The same entity performs the scan and the interpretation |
| 76 / 77 | Repeat procedure | A medically necessary repeat on the same day, by the same or a different physician |
For bilateral studies, most payers want two lines, 73721-RT and 73721-LT, each with one unit. Some accept modifier 50. Follow the payer’s instructions and the bilateral indicator in the Medicare fee schedule file.
Missing or conflicting modifiers often lead to CO-4 denials, where the procedure code is inconsistent with the modifier or a required modifier is missing.
Do not bill the global code when you only read the study. If a hospital or another entity owns the scanner, it bills the technical component. Billing 73721 globally in that case duplicates payment and leads to recoupment.
2026 Medicare Payment for CPT 73721
The table below uses the 2026 Medicare Physician Fee Schedule relative value units for 73721 and the 2026 conversion factor of $33.4009. These are national amounts before the geographic practice cost index (GPCI) adjustment, so your local MAC rate will differ.
| Component | Total RVUs | 2026 national amount | Who bills it |
|---|---|---|---|
| 73721 global | 6.12 | $204.41 | Office or independent imaging center that scans and reads |
| 73721-26 | 1.88 | $62.79 | Radiologist reading the study |
| 73721-TC | 4.24 | $141.62 | Owner of the equipment and staff |
Formula. Total RVUs × conversion factor = national amount. For the global service, 6.12 × $33.4009 = $204.41. Your actual payment applies your locality’s GPCIs and patient cost sharing.
In a hospital outpatient department, the hospital is paid for the technical side under the Outpatient Prospective Payment System, and the radiologist bills 73721-26 under the fee schedule. Commercial rates depend on your contract, so compare each payment to your fee schedule as described in our guide to contractual adjustments.
Multiple Procedure Payment Reduction for Imaging
When the same physician or group performs more than one advanced imaging study on the same patient in the same session on the same day, Medicare reduces payment for the lower-priced studies. According to Noridian, the technical component of each additional study is paid at 50 percent, and the professional component at 95 percent, for codes with a multiple procedure indicator of 4.
Worked example: bilateral knee MRI, same session. An independent imaging center bills 73721-RT and 73721-LT globally. The first knee is paid at the full national amount of $204.41. On the second knee, the technical component is reduced to $70.81 (50 percent of $141.62) and the professional component to $59.65 (95 percent of $62.79), for $130.46. The national total is $334.87 rather than $408.82, before geographic adjustment.
Prior Authorization and Radiology Benefit Managers
Original Medicare does not require prior authorization for a lower extremity MRI. CMS also paused the Appropriate Use Criteria program for advanced diagnostic imaging and rescinded its regulations in the 2024 fee schedule final rule, so Medicare claims no longer need AUC consultation data.
Medicare Advantage plans, Medicaid managed care plans and most commercial plans do require approval, and many delegate the review to a radiology benefit manager (RBM) such as eviCore or Carelon. These reviewers apply clinical criteria, which often ask whether the patient has had recent X-rays and a trial of conservative treatment for non-traumatic pain.
- Check the requirement. Confirm whether the plan or its RBM requires approval for 73721, and whether the ordering or rendering provider must request it. Our guide to preventing insurance verification errors covers what to confirm.
- Request the exact code. Ask for the specific code and side that will be performed, including contrast.
- Send the clinical story. Include the exam findings, symptom duration, prior imaging and treatment tried.
- Match the claim. Make sure the code, side, dates and rendering site on the claim match the approval.
- Fix changes fast. If the study changes to 73723 or the other side, update the authorization before the claim goes out.
When the authorization number is missing or does not match, payers commonly deny with CARC 15; see our CO-15 denial guide. If a study had to be done before approval, some plans offer a retro authorization process within a short window.
Medical Necessity and ICD-10-CM Linkage
The diagnosis must explain why the MRI was needed, and it should be as specific as the record allows, including laterality and encounter type; our knee pain ICD-10 code guide explains when to use M25.56- versus a definitive diagnosis. These FY2027 ICD-10-CM codes are common examples:
| ICD-10-CM | Description | Typical study |
|---|---|---|
| S83.241A | Other tear of medial meniscus, current injury, right knee, initial encounter | 73721-RT |
| S83.511A | Sprain of anterior cruciate ligament of right knee, initial encounter | 73721-RT |
| M25.561 | Pain in right knee | 73721-RT, often after X-rays and conservative care |
| S93.421A | Sprain of deltoid ligament of right ankle, initial encounter | 73721-RT |
| M87.051 | Idiopathic aseptic necrosis of right femur | 73721-RT (hip) |
A side mismatch, such as a left knee diagnosis on a 73721-RT line, is an easy edit for payers to catch. A diagnosis that does not support the study can lead to a CO-11 denial.
Documentation Checklist for 73721
- A signed order from the treating provider stating the body part, side and clinical reason.
- A report identifying the joint and side imaged, the technique, and whether contrast was used.
- The radiologist’s signed interpretation with findings and impression.
- The authorization number, approved code and approved dates, when the plan requires approval.
- For arthrography, a separate note for the injection procedure and the contrast used.
Need cleaner MRI claims and fewer authorization denials? Steady Medical Billing’s radiology billing team handles component billing, modifiers and payer authorizations for imaging centers and radiology groups. Orthopedic groups can also see our orthopedic billing services.
Frequently Asked Questions
What is CPT code 73721?
CPT 73721 is magnetic resonance imaging of any joint of the lower extremity, such as the hip, knee or ankle, without contrast material. With contrast is 73722, and without followed by with contrast is 73723.
What is the difference between 73718 and 73721?
73721 is for MRI of a lower extremity joint. 73718 is for MRI of the lower extremity other than a joint, such as the thigh or calf. Both are without contrast.
How much does Medicare pay for 73721 in 2026?
Using 6.12 total RVUs and the 2026 conversion factor of $33.4009, the national amount is about $204.41 globally, $62.79 for the professional component (26) and $141.62 for the technical component (TC), before geographic adjustment.
Does a knee MRI need prior authorization?
Original Medicare does not require prior authorization for 73721. Most Medicare Advantage, Medicaid managed care and commercial plans do, often through a radiology benefit manager, so verify the requirement before scheduling.
How do I bill a bilateral knee MRI?
Most payers want two lines, 73721-RT and 73721-LT, with one unit each, though some accept modifier 50. Under Medicare, the multiple procedure payment reduction cuts the second study technical component to 50 percent and the professional component to 95 percent.
