Knee and Hip Replacement Billing Errors

Knee and hip replacement are among the most common major surgeries in the United States, with over one million performed each year. They are also among the most expensive. The total cost of a knee replacement averages $30,000 to $50,000, and a hip replacement runs $32,000 to $55,000 or more. For patients with high-deductible health plans, out-of-pocket costs can reach $5,000 to $10,000 even with insurance.

The complexity of joint replacement billing creates fertile ground for errors. A single surgery generates charges from the orthopedic surgeon, the assistant surgeon (if one is used), the anesthesiologist, the hospital facility, the implant manufacturer (passed through the hospital), the physical therapist, the lab, and sometimes a post-acute rehab facility. Each provider bills separately, and each bill can contain errors.

This guide covers the seven most common billing errors on knee and hip replacement bills and shows you exactly what to look for.

How joint replacement billing works

Joint replacement surgery is typically billed under a "global surgical package" for the surgeon's professional fee. The global package bundles certain services into a single CPT code for a set number of days before and after surgery.

Key CPT codes:

• 27447 -- Total knee arthroplasty (total knee replacement). Medicare rate: approximately $1,400-$1,800 (surgeon's professional fee only).
• 27446 -- Unicompartmental knee arthroplasty (partial knee replacement). Medicare rate: approximately $1,200-$1,500.
• 27130 -- Total hip arthroplasty (total hip replacement). Medicare rate: approximately $1,400-$1,800.
• 27132 -- Revision total hip arthroplasty (conversion of previous surgery). Medicare rate: approximately $1,800-$2,200.

What the global surgical package includes (for 90-day global period):

• The surgery itself
• Pre-operative evaluation on the day before or day of surgery
• All post-operative visits related to the surgery for 90 days
• Post-operative pain management provided by the surgeon
• Routine wound care and suture removal
• Management of complications that do not require a return to the operating room

What is NOT included and is billed separately:

• Hospital facility charges (room, OR time, nursing, supplies)
• Anesthesia
• The implant itself (billed through the hospital)
• Physical therapy (both inpatient and outpatient)
• Lab work and imaging
• Assistant surgeon fees (if applicable)
• Post-acute care at a rehab facility

Understanding this split is essential. Many billing errors involve charging separately for services that are already included in the global surgical package.

Bundled vs. unbundled surgical charges

The most common billing error category for joint replacement is unbundling: charging separately for services that should be part of the global surgical package or the hospital's DRG payment.

Common unbundling errors:

• Post-operative office visits billed within the 90-day global period. Under the global surgical package, all routine follow-up visits with the surgeon for 90 days after surgery are included in the surgical CPT code. If your surgeon bills a separate E/M visit code (99213, 99214) for a routine 2-week or 6-week post-op check, that charge should not appear. The only exception is if the visit is for a new, unrelated problem (in which case modifier -24 should be used).
• Wound care billed separately. Staple removal, incision checks, and dressing changes after joint replacement are part of the global package. Separate charges for wound care CPT codes (97597, 97598) within the 90-day period are usually incorrect.
• Surgical preparation charged as a separate procedure. Skin prep, draping, and positioning are part of the facility fee and the surgical procedure. They should not appear as separate line items.
• Intraoperative imaging. Fluoroscopy or X-ray guidance used during surgery (76000, 76001) is typically bundled into the surgical procedure for joint replacement. Check NCCI edits for the specific code pair.

Use our NCCI code pair checker to verify whether any two codes on your bill should have been bundled together.

Implant upcharges

The prosthetic implant is one of the largest single costs in a joint replacement -- typically $5,000 to $15,000 for the hardware alone. For hospital inpatients, the implant cost is supposed to be included in the DRG (diagnosis-related group) payment that the hospital receives from the insurer. For outpatient procedures, it may be billed separately.

What to watch for:

• Implant charged separately on inpatient stays. If your joint replacement was performed as an inpatient (DRG 469 or 470 for major joint replacement), the hospital receives a bundled DRG payment that includes the implant. A separate implant charge on your itemized bill should not result in additional patient cost-sharing beyond what the DRG requires.
• Premium implant upcharge without disclosure. Some surgeons use premium or brand-name implants that cost more than standard implants. If the hospital passes through a higher implant cost that increases your bill, you should have been informed about the choice before surgery. Ask whether a standard implant was an option.
• Implant markup. Hospitals mark up implant costs, sometimes by 200-400% over the manufacturer's price. While this is legal, it contributes to inflated facility bills. If you are on a high-deductible plan and paying a significant portion of the facility fee, the implant markup directly affects your out-of-pocket cost.
• Bilateral surgery implant charges. If you had both knees or both hips replaced in the same surgery, there should be two sets of implant charges. But make sure only two are billed -- not three or four.

Under the Hospital Price Transparency Rule (effective January 1, 2021), hospitals are required to publish the prices of implants and all other services. You can look up your hospital's published prices before surgery to get an estimate of the implant cost. This also gives you a baseline for checking the bill afterward.

Physical therapy charges during hospital stay

After joint replacement surgery, physical therapy begins within hours -- typically the same day or the day after surgery. You will work with a physical therapist during every day of your hospital stay. How this PT is billed depends on whether you are classified as inpatient or outpatient.

Inpatient: If you are admitted as an inpatient (most total joint replacements), physical therapy during the hospital stay is typically included in the DRG payment. It should not generate separate CPT-coded PT charges on your bill. If you see CPT codes like 97110, 97140, or 97530 dated during your inpatient stay, those charges may be incorrectly unbundled from the DRG.

Outpatient: Some knee and hip replacements are now performed in ambulatory surgery centers or as hospital outpatient procedures with same-day discharge. In these cases, PT provided the same day may be billed separately -- but verify that the charges are reasonable and that the units reflect actual treatment time.

Post-discharge outpatient PT: Physical therapy after you leave the hospital is a separate service and is billed normally under PT CPT codes. These charges are legitimate, but you should still verify them using the guidance in our physical therapy billing errors guide.

Assistant surgeon fees

Some joint replacement surgeries require an assistant surgeon. When present, the assistant surgeon bills separately using the same surgical CPT code as the primary surgeon but with modifier -80 (assistant surgeon) or -82 (assistant surgeon when qualified resident is not available). The assistant surgeon's fee is typically 16-20% of the primary surgeon's fee.

What to check:

• Was an assistant surgeon necessary? Medicare and many insurers require documentation of medical necessity for an assistant surgeon. If the surgery was straightforward and performed at a teaching hospital with residents available, an assistant surgeon charge may not be covered.
• Correct modifier. The assistant surgeon should bill with modifier -80. If the claim shows the full surgical code without the assistant modifier, it may appear as a duplicate of the primary surgeon's charge.
• Assistant surgeon who is actually a resident. At teaching hospitals, residents often assist with surgeries as part of their training. Residents cannot bill assistant surgeon fees. If you see an assistant surgeon charge at a teaching hospital, verify that the assistant was a separately credentialed surgeon, not a resident.
• Multiple assistant surgeon charges. Routine knee or hip replacement should require at most one assistant surgeon. Multiple assistant surgeon bills are a red flag.

Anesthesia time billing errors

Anesthesia for joint replacement is billed with a base unit value specific to the surgical procedure plus time units based on the actual duration of anesthesia. The base units for total knee and hip replacement are typically 7-8 base units. Time is billed in 15-minute increments.

Typical anesthesia billing:

• Base units: 7-8 (set by the procedure code)
• Time units: 6-10 (for a 90-150 minute procedure)
• Total units: 13-18
• Rate per unit: $20-$70 depending on the payer and geographic area
• Total anesthesia charge: approximately $600-$1,500

Common anesthesia billing errors:

• Inflated time. A total knee replacement takes approximately 60-120 minutes of surgical time. Anesthesia time includes some pre-operative and post-operative minutes (induction, emergence), but should generally be 90-150 minutes total. If the bill shows 240 minutes (16 time units), the time is inflated. Request the anesthesia record, which documents exact start and end times.
• Wrong base units. Each surgical procedure has a defined number of base units set by the ASA (American Society of Anesthesiologists). The base units should match the procedure performed. If the base unit value on the claim is higher than what is published for the procedure, it is an error.
• Separate charges for nerve blocks. Regional anesthesia (nerve blocks) used in conjunction with general anesthesia for joint replacement may or may not be separately billable depending on payer policies. Some insurers bundle the nerve block into the primary anesthesia service. Check your EOB to see how the nerve block was processed.
• Anesthesia for separately billed post-op nerve block. If a post-operative continuous nerve block catheter was placed for pain management, the initial placement may be a separate charge, but the anesthesia time for the primary surgery should not include the time spent placing the catheter.

Post-surgical lab work double billing

After joint replacement surgery, routine lab work is ordered to monitor your recovery -- typically a complete blood count (CBC, 85025) and a basic metabolic panel (BMP, 80048) or comprehensive metabolic panel (CMP, 80053). Errors in lab billing after surgery are common.

What to watch for:

• Duplicate labs on the same day. One CBC per day is standard post-operatively unless there is active bleeding or a specific clinical concern. Two CBCs on the same date should have a clinical justification. The same applies to metabolic panels.
• Lab panel plus individual components. If your bill shows a CMP (80053) plus a separate glucose (82947) or electrolyte panel (80051) on the same date, the individual tests are already included in the CMP. This is an unbundling error.
• Labs ordered but cancelled. A doctor may order repeat labs, then cancel the order when the patient is doing well. The charge may still post. Cross-reference lab charges with your medical records to verify each test was actually performed.
• Pre-admission testing double billed. Blood work done during your pre-surgical testing appointment (typically a few days before surgery) should not be repeated and billed again on the day of surgery unless there is a specific clinical reason.

Rehab facility charges after discharge

Some patients are discharged from the hospital to a skilled nursing facility (SNF) or inpatient rehabilitation facility (IRF) for continued recovery before going home. This generates a separate set of charges with its own billing complexities.

What to know:

• Medicare's 3-day rule. For Medicare patients, coverage in a SNF requires a qualifying inpatient hospital stay of at least 3 consecutive days (not counting the discharge day). If your hospital stay was shorter than 3 days, or if you were on observation status (not inpatient), your SNF stay may not be covered by Medicare Part A. This is one of the most financially devastating classification issues for Medicare beneficiaries undergoing joint replacement.
• Overlap charges. Your hospital charges should end on your discharge date. Your rehab facility charges should begin on your admission date to that facility. If both bills show charges for the same date, there may be overlap.
• Services billed twice. Physical therapy, lab work, and medications provided during the rehab facility stay should be billed by the rehab facility, not carried over from the hospital's billing system. Check for duplicate charges across the two facilities.
• Length of stay. Count the actual days you spent at the rehab facility and compare against the billed days. Errors in admission and discharge dates can add or subtract days from the bill.

How to check your joint replacement bill

1. Collect all bills. You may receive bills from the hospital, the orthopedic surgeon, the assistant surgeon, the anesthesiologist, the physical therapist, the lab, and the rehab facility. Request fully itemized statements from each. For help reading them, see our guide to reading itemized medical bills.
2. Check the surgical code. Verify the CPT code matches the surgery performed -- knee (27447) or hip (27130), total or partial, primary or revision. Use our CPT lookup tool to check the code description and Medicare rate.
3. Look for global package violations. Any charges from the surgeon's office for routine follow-up visits within 90 days of surgery should already be included in the surgical fee.
4. Verify anesthesia time. Request the anesthesia record. Compare the documented start and end times to the billed time units.
5. Check the implant charges. Verify that the implant is not billed separately if you were an inpatient (DRG payment should include it).
6. Verify inpatient PT billing. If you were an inpatient, PT during the hospital stay should be included in the DRG. Separate PT charges on the hospital bill for dates during your inpatient stay are suspect.
7. Check lab billing. Look for duplicate labs on the same date and for individual lab tests that are already included in a panel code.
8. Verify admission status. If you are a Medicare patient, confirm that your hospital stay was classified as inpatient (not observation) and that it met the 3-day minimum if you went to a SNF.
9. Run the math. Use our bill math checker to verify the totals on each bill.

What to do when you find an error

1. Start with the specific billing department. For surgeon billing errors, call the surgeon's office. For facility errors, call the hospital billing department. For anesthesia, contact the anesthesia group. Be specific about the line item, the date, and the error.
2. Request your operative report. This document details exactly what was done during surgery, including the implant used, the assistant surgeon (if any), and the surgical time. It is the definitive record for verifying surgical charges.
3. Contact your insurer. For complex billing disputes involving multiple providers, your insurer's member services team can coordinate reviews across all claims associated with the surgery.
4. Send written disputes. For errors that are not resolved by phone, send formal dispute letters to each provider. Our dispute letter generator can create letters with the correct format and citations.
5. Ask about bundled payment programs. Some hospitals and insurers offer bundled payment arrangements for joint replacement that include all services (surgery, hospital stay, PT, follow-up) in a single negotiated price. If your insurer has such a program, verify that you were enrolled and that the bundled rate was applied.
6. Negotiate. Joint replacement is one of the procedures where price negotiation before surgery can save thousands. After surgery, if you are facing a large bill, ask about payment plans, financial assistance, or prompt-pay discounts. Many hospitals offer 10-20% discounts for lump-sum payment.

For more on the dispute process, see our universal dispute guide and dispute letter template. For background on all types of medical billing errors, see our complete guide to medical billing errors. For state-specific billing protections, see our state rights guide.

Disclaimer: This guide is for educational purposes only and does not constitute legal, financial, or medical advice. Surgical costs, billing practices, and insurance coverage vary by hospital, surgeon, state, and insurance plan. Cost figures cited are national averages and may not reflect your specific situation. Medicare rules described here are based on CMS guidelines as of early 2026. Consult a licensed professional for advice specific to your circumstances.