Short answer: Medicare covers medically necessary knee replacement surgery. Coverage can involve Part A, Part B, or both. The amount owed depends on whether the person is formally admitted as an inpatient or receives the surgery as an outpatient.
Original Medicare coverage
Medicare covers many medically necessary inpatient and outpatient surgical procedures. Knee replacement can include the surgeon, hospital or ambulatory surgical center, anesthesia, implants, imaging, therapy, and follow-up services. Each service is subject to its own billing and coverage rules.
Part A generally covers a qualifying inpatient hospital stay after a formal admission order. Part B covers physician services and outpatient hospital or ambulatory surgical center services. Staying overnight does not by itself make a person an inpatient.
Eligibility and limits
The treating surgeon must determine that the procedure is medically necessary. The medical record may include symptoms, examination findings, imaging, functional limitations, and treatment history. Medicare does not require the same treatment sequence in every case, but a service must be reasonable and necessary for the individual condition.
Coverage of rehabilitation after surgery depends on where it is provided and whether separate requirements are met. A knee replacement does not automatically qualify someone for a skilled nursing facility stay.
Costs
For an inpatient admission, the Part A deductible and benefit-period rules apply. Part B generally covers surgeon and other professional services, with the Part B deductible and coinsurance. For outpatient surgery, the beneficiary may owe physician coinsurance and a facility copayment. Drugs, equipment, and therapy may create additional charges.
Medicare Advantage
Medicare Advantage plans cover medically necessary knee replacement but may require network surgeons and facilities, prior authorization, or a referral. Copayments can differ by setting.
What to do next
- Ask whether the procedure is planned as inpatient or outpatient.
- Request estimates from the surgeon, facility, and anesthesia group.
- Ask what therapy, equipment, and follow-up care are expected.
- For Medicare Advantage, obtain required authorization before surgery.
Sources
- Medicare.gov: Surgery
- Medicare.gov: Inpatient or outpatient status
- Medicare.gov: Inpatient hospital care
Last reviewed: August 2026. Medicare rules and plan benefits can change.