How Medicare Covers Knee Replacement Surgery
Knee replacement surgery, also called total knee arthroplasty, is a procedure where a surgeon removes damaged bone and cartilage from your knee joint and replaces it with artificial parts made of metal and plastic. Medicare Part B helps cover the costs of this surgery when your doctor determines it is medically necessary. According to the Centers for Medicare and Medicaid Services (CMS), knee replacements are among the most common surgeries performed on Medicare beneficiaries, with over 700,000 procedures performed annually in the United States.
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Medicare Part B typically pays 80 percent of the approved amount for knee replacement surgery after you meet your annual deductible. You are responsible for paying the remaining 20 percent, which is called coinsurance. The approved amount is what Medicare decides is a reasonable charge for the procedure in your area. This means your actual out-of-pocket cost depends on what your surgeon's charges are and whether they accept Medicare's approved amount.
It is important to understand that Medicare coverage applies to the surgery itself, but there are many related costs involved in the process. These include pre-surgery evaluations, imaging tests like X-rays and MRIs, the hospital or surgical facility fees, the surgeon's fee, anesthesia, and post-surgery rehabilitation. Each of these services may have different coverage rules. Some services may be covered by Medicare Part A if you have inpatient surgery, while others fall under Part B if performed in an outpatient setting.
The way Medicare pays also depends on where you receive your surgery. If you stay overnight in a hospital, Medicare Part A covers hospital costs. If your surgery is performed at an outpatient surgical center or hospital without an overnight stay, Medicare Part B applies to professional fees, and the facility may bill under different rules. Many knee replacements today are performed as outpatient procedures, which means you go home the same day.
Practical Takeaway: Before scheduling knee replacement surgery, ask your surgeon's office what the total charges will be and confirm that your surgeon accepts Medicare's approved amount. Request an itemized estimate showing all costs—surgery, facility, anesthesia, and imaging—so you understand what your 20 percent coinsurance obligation will be.
Medical Necessity and Pre-Surgery Requirements
Medicare will not pay for knee replacement surgery unless your doctor documents that it is medically necessary. Medical necessity means that the procedure is appropriate treatment for your condition based on current medical practice and evidence. Simply having knee pain or arthritis is not enough on its own. Your doctor must show that you have a condition causing significant functional impairment and that surgery is the right treatment after other options have been tried.
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Most patients seeking knee replacement have osteoarthritis, which is the wearing down of cartilage in the joint over time. According to the National Institutes of Health, osteoarthritis affects more than 32 million American adults. Other conditions that may lead to knee replacement include rheumatoid arthritis, traumatic injury to the knee, or avascular necrosis (death of bone tissue). Your doctor will examine your knee, review imaging results, and consider your age, overall health, and lifestyle to determine if surgery is appropriate.
Before approving knee replacement surgery, Medicare often requires that you try less invasive treatments first. These conservative treatments typically include physical therapy, weight management, anti-inflammatory medications, and injections such as corticosteroids or hyaluronic acid. Your doctor's records should document how long you tried these treatments, how much they helped, and why they are no longer effective for your condition. Some surgeons may require patients to complete a certain number of physical therapy sessions or wait a specific time period before moving forward with surgery.
Your surgeon will also order imaging tests to confirm the degree of damage to your knee. X-rays are the standard tool for showing bone-on-bone arthritis and damage to the joint structure. An MRI may be ordered if there are questions about soft tissue damage. Your medical history is reviewed to identify any conditions that might complicate surgery, such as heart disease, diabetes, or obesity. If you have significant health risks, your doctor may order additional tests like an EKG or blood work. Medicare covers these diagnostic tests when ordered by your physician as part of the evaluation for surgery.
Practical Takeaway: Work with your doctor to document your treatment history. Keep records of all conservative treatments you have tried, including dates and results. If you have seen multiple doctors or received care at different facilities, gather these medical records and bring them to your surgeon's office, as they help demonstrate medical necessity to Medicare.
Understanding Your Out-of-Pocket Costs
After you meet your Medicare Part B annual deductible, you pay 20 percent coinsurance for knee replacement surgery and related services covered by Part B. For 2024, the Part B deductible is $240. Once you have paid this amount out of pocket for Part B services, Medicare begins paying its 80 percent share. However, your actual costs depend on whether your surgeon and facility accept Medicare's approved amount.
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If your surgeon is a Medicare participating provider, they accept Medicare's approved amount as payment in full. This means you pay 20 percent of that approved amount, and the surgeon cannot bill you for the remaining balance. If your surgeon is a non-participating provider, they can charge up to 15 percent more than Medicare's approved amount. This additional cost—called the limiting charge—comes directly out of your pocket and does not count toward your deductible or out-of-pocket maximum. It is crucial to ask whether your surgeon participates in Medicare before scheduling surgery.
To find out Medicare's approved amount for knee replacement in your area, you can use the Medicare Physician Fee Schedule Lookup tool on the CMS website. As an example, Medicare's approved amount for a total knee replacement in many areas ranges from approximately $12,000 to $14,000 for the surgeon's fee alone. Your 20 percent coinsurance on a $13,000 approved amount would be $2,600. However, this does not include facility fees, anesthesia, or other related services, which add significantly to your total costs.
If you have supplemental insurance (often called Medigap), it may help pay some or all of your coinsurance and deductible costs. The amount of coverage depends on which Medigap plan you have. If you are in a Medicare Advantage plan instead of Original Medicare, your costs work differently. Medicare Advantage plans set their own deductibles and coinsurance amounts, which can vary widely. Some plans may offer lower out-of-pocket maximums, which means your costs are capped at a certain amount per year.
Practical Takeaway: Contact your surgeon's billing department and ask for a pre-surgery cost estimate that includes the surgeon's fee, facility fee, anesthesia, and any other charges. Ask specifically whether your surgeon participates in Medicare. If you have Medigap or Medicare Advantage coverage, call your insurance plan to find out how much they will pay toward the surgery costs after Medicare pays its share.
Hospital Stay Versus Outpatient Surgery Coverage
Knee replacement surgery can be performed in two main settings: as an inpatient procedure where you stay overnight in a hospital, or as an outpatient procedure where you return home the same day. The setting affects how Medicare pays for your care and what costs you are responsible for. Understanding the difference helps you plan for your expenses and recovery.
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For inpatient knee replacement, you are admitted to the hospital and typically stay for one to three days following surgery. Medicare Part A covers inpatient hospital costs including your hospital room, meals, nursing care, and hospital services. Instead of paying coinsurance for each service, you pay a single inpatient deductible ($1,632 in 2024) for the first 60 days of hospitalization in a benefit period. After you pay this deductible, Medicare covers all approved inpatient costs with no additional coinsurance. If your stay extends beyond 60 days, different cost-sharing rules apply, but most knee replacements result in shorter stays.
Outpatient knee replacement is performed at a hospital outpatient department or ambulatory surgical center, and you go home the same day. In this case, Medicare Part B applies to the professional fees (surgeon, anesthesiologist), and facility charges are handled differently depending on the type of facility. At a hospital outpatient department, you typically pay a copayment for the outpatient visit plus 20 percent coinsurance for services. At an ambulatory surgical center, costs are usually lower overall because these facilities have less overhead than hospitals. According to CMS