Ultimate Guide to CPT Code 73721: Codes, Billing & Payments Explained!

The data that’s tracked by the OECD (Organization for Economic Co-operation and Development) and reported by Statista shows that nearly 40 million MRI scans are performed in the United States every year. Many of them are joint scans, and that is exactly where CPT 73721 comes in.

Every one of those lower-joint scans needs the right code on the claim. If the code is wrong, the payment is late or never comes.

This guide is for medical billers and coders, and practice managers who want this code right the very first time.  In this blog, we cover what it means, when to use it, how to bill it, and what exactly it pays.

What Is CPT 73721 in Medical Billing?

CPT 73721 is for all joints of the lower extremity without contrast. It can be a joint at the hip, knee, ankle, or foot. The code does not change depending on the joint. It only varies according to contrast.

This scan is ordered when an X-ray does not provide an explanation for the problem. Common reasons are:

• Knee pain after a twist, fall, or sports injury
• Suspected meniscus, ACL, MCL, or PCL tears
• Hip pain with no clear cause
• Ankle sprains that don’t heal
• Tendon problems and cartilage damage
• Swelling or fluid around a joint

MRI shows soft tissue like ligaments, cartilage, and tendons far better than X-ray does. That is why it is the go-to scan for joint injuries.

73721 CPT Description in Simple Words

The official 73721 CPT description, from the AMA CPT code set, reads: “Magnetic resonance (e.g., proton) imaging, any joint of lower extremity; without contrast material.”

The code counts one joint. For patients who have a knee scan and an ankle scan in the same visit, scan each knee and ankle and bill on each occasion.

When to Use CPT Code 73721 (and When Not To)

Use CPT code 73721 when all of these are true:

• The scan is of a lower-extremity joint
• No contrast was used at all
• There is a signed order from the treating provider
• The diagnosis supports medical necessity

Don’t use it when:

• Contrast was given. That moves you to 73722 or 73723.
• The area scanned is not a joint, like the thigh or lower leg. Those fall under 73718 to 73720.
• What the order meant is one thing, and what the scan meant is another; make sure to always bill for what was actually performed.

Related Codes at a Glance

The 73721 vs 73723 mix-up is the classic one. If the radiologist scans without dye and then repeats with dye, that is 73723 alone. Don’t add 73721 on top.

Procedure Code 73721: Technical and Professional Split

Procedure code 73721 has two parts, and who bills which one depends on who owns the machine.

• Technical component (TC): the machine, room, MRI tech, and supplies
• Professional component (26): the radiologist reading the images and writing the report
• Global (no modifier): one party does both and bills the full amount

Here’s how it works. The MRI is own by a hospital, and it bills TC. The radiologist who reads the images bills with modifier 26. In the case of an imaging center that owns its own machine and has its own dedicated radiologist, it charges globally.

One of the most frequent mistakes made in imaging claims is not including the modifier. The payer is seeing 2 claims, both of which appear global, pays one, and denies the other. When the facility and the radiologist are separate, each must bill only their own part, using TC or 26.

Also add side modifier: RT for right, LT for left. Some payers want 2 lines; some 50 modifier for both sides. Please read the payer policy before submission.

What Billers Commonly See with This Code

Some problems repeat again and again on knee and ankle MRI claims:

• The order says “MRI knee” but doesn’t say which side, so the claim gets held
• The scan was done with contrast, but the claim went out under 73721
• Prior auth was approved for one joint, but two joints were scanned
• The diagnosis on the claim is “knee pain,” which is too vague for the payer

None of these are hard to fix. They just need someone to check before submission instead of after denial.

Step-by-Step Billing for the 73721 CPT Code

Below, each step is explain in a detailed way, from the very first step to the end, when your billing process is complete

Step 1: Verify Insurance Before the Scan

Ensure that the plan is in place and outpatient MRI is included. Make sure there is no surprise bill after the scan, as everyone will be cover by the deductible and copay, and will always know which network the health care provider is in.

Step 2: Get Prior Authorization

There are numerous commercial and Medicare Advantage plans that require approval prior to an MRI. Make sure to send the order and clinical notes to the payer, and save the auth number and approved dates.

Step 3: Check the Order

The order needs to specify the joint, side (right or left), and reason for scan. If something is missing, ask the provider to correct it prior to billing.

Step 4: Link the Right ICD-10 Code

Choose the most specific diagnosis possible that the doctor’s notes support. The term “knee pain” is ambiguous, and a meniscus tear is a medical necessity and reduces the possibility of medical denial.

Step 5: Add the Correct Modifiers

For the technical part, use TC, and for the radiologist’s reading, use 26. Skip both only when you bill global. Include RT/LT on the side.

Step 6: Attach the Report if Required

Some payers require the radiology report to be attached to the claim. Submit the signed report with findings and impression so that the reviewer can view the report and confirm that the scan is a match to the code billed.

Step 7: Submit Before the Deadline

The filing time limits are between 90 days and one year, depending on the payer. Send clean claims on time, and then follow up on them to ensure that no claims go unpaid.

Payments: What Does CPT 73721 Pay?

Payment depends on the payer, the state, and where the scan is done. These are approximate Medicare ranges only. 

There are a number of different commercial plans that can offer higher payment than Medicare. Payments are reduces if documentation is incomplete, the modifier is incorrect, or another imaging service is co-packaged on the same day.  Many USA medical billing companies track payer-specific imaging rates so practices know what to expect before the claim goes out.

ICD-10 Codes Often Paired With 73721

Common Denials and How to Fix Them

Most of these can be stopped at the front desk. It is much cheaper than working them in the appeals queue.

Workers’ Comp and Injury Cases

A large number of lower joint MRIs are from on-the-job injuries and claims. A worker twists his knee on the job site, and the MRI is order within days. These are claims that run on a different level. States have different fee schedules (in California, the Official Medical Fee Schedule), utilization review is often used, and the bill is submitted to the employer’s carrier, rather than to the patient’s health plan.

That is the reason why many imaging facilities or clinics pass on these claims to the workers compensation billing services. There are more stringent deadlines, more forms, and one incorrect entry can delay payment for months.

Why Outsourcing Is the Smart Choice for CPT 73721 Billing

Imaging billing is a complex operation with numerous moving parts. One claim may require a diagnosis to establish medical necessity, an RT or LT side code, a TC, or 26 modifiers, and may require prior authorization. If any of those are not in place, then it’s back to a denied claim. 

All of this has to be managed by an in-house team along with front desk responsibilities, patient calls, and payer updates, and it’s easy to fall prey to error. Outsourcing to a radiology billing company puts the whole job in the hands of people who do this every day. They already have an understanding of the payer rules, don’t wait for claims to be lost, and don’t let unpaid claims accumulate. 

You also save on staff turnover, software, training, and staff salaries. Most importantly, your team’s time is recovered to focus on patients, claims are submitted clean, and payments are received quicker. 

Wrapping It Up

CPT 73721 looks like a simple code, but the money is in the details. Select the appropriate joint, confirm no contrast was administered, attach the proper modifiers, attach a specific diagnosis, and request prior authorization prior to scanning. Apply those to the initial claim, and the majority of claims are paid. If you make one mistake, you’ll be stuck in the denial line for a few weeks waiting for the payment that should have already been processed.

Fortunately, you can avoid nearly all of the issues in this guide before the claim leaves the gates. Checking with the front desk will save exponentially more time than an appeal later on. 

FAQs

1. What is CPT code 73721?

CPT code 73721 is the billing code for an MRI of any lower extremity joint, such as the hip, knee, ankle, or foot, done without contrast dye.

2. What is the difference between CPT 73721 and 73722?

The only difference is contrast. CPT 73721 is an MRI without contrast dye, while 73722 is an MRI of the same joints done with contrast dye.

3. Does CPT 73721 require prior authorization?

Often yes. Many commercial and Medicare Advantage plans require prior authorization for MRI scans. Original Medicare usually does not, but always check the payer’s policy before the patient is scan.

4. How much does Medicare pay for CPT 73721?

The global Medicare payment is roughly $190 to $250, depending on location and year. Check the current CMS Physician Fee Schedule for the exact amount in your area.

5. What modifiers are used with CPT 73721?

Common modifiers are TC for the technical part, 26 for the radiologist’s reading, and RT or LT for the side. Some payers accept modifier 50 for bilateral scans.

6. Can you bill CPT 73721 twice on the same day?

Yes, but only for two different joints, like a knee and an ankle, and both scans must be documented. You cannot bill it twice for the same joint.

7. Is CPT 73721 a knee MRI?

It can be. CPT 73721 covers a knee MRI done without contrast, and it also covers hip, ankle, and foot joint MRIs done without contrast.

8. Why was my CPT 73721 claim denied?

Common reasons are missing prior authorization, a vague diagnosis, a missing modifier, a duplicate claim, or billing 73721 when contrast was actually used. Check the denial code first.