- Knee replacement resurfaces a worn joint with metal and plastic components; it is almost always done for end-stage osteoarthritis after conservative care (PT, weight management, medication, injections) has stopped controlling pain and function.
- A partial (unicompartmental) replacement treats one worn section of the knee, while a total knee replacement resurfaces the whole joint and is far more common.
- Recovery is gradual: most people walk with an aid within days, resume many daily activities by 3-6 weeks, and continue improving for several months, with driving typically returning around 4-6 weeks.
- Blood clots (DVT/PE) are among the most common serious risks — seek emergency care for sudden shortness of breath, chest pain, or new calf pain and swelling — alongside infection (under 2%) and, rarely, implant problems.
- Over 90% of modern knee implants are still working at 15 years, but younger and heavier patients wear them faster, so surgeons often weigh timing carefully.
- This article is educational and not a substitute for professional medical advice; every decision and your recovery plan should be directed by your orthopedic surgeon.
More than 700,000 total knee replacements are performed in the United States each year, making it one of the most common elective orthopedic procedures, according to the American Academy of Orthopaedic Surgeons. A knee replacement resurfaces a worn-out joint with metal and polyethylene components, and most patients return to walking, gardening, and low-impact recreation within a few months. The decision is rarely urgent, but waiting too long can make recovery slower. This guide walks through how the surgery is done, what realistic recovery looks like, the risks to watch for, and how to weigh whether total knee arthroplasty fits your situation. It is educational only — every step described here is a decision to make with your orthopedic surgeon.
What Knee Replacement Is and Who Needs It
Total knee arthroplasty (TKA) replaces the damaged surfaces of the femur, tibia, and often the patella with prosthetic components. Surgeons may use a partial (unicompartmental) replacement when only one section of the joint is worn, but the total version is far more common. The procedure is almost always performed for end-stage osteoarthritis, although rheumatoid arthritis, post-traumatic arthritis, and avascular necrosis are other indications listed by the Mayo Clinic.
Surgeons usually consider the procedure when conservative measures have failed. That means physical therapy, weight management, NSAIDs, corticosteroid or hyaluronic acid injections, and bracing have stopped controlling pain or preserving function. Candidates typically have severe knee pain or stiffness that limits everyday activities — trouble climbing a flight of stairs, sleeping through the night, or walking a few blocks — along with pain at rest or knee deformity that no longer responds to medication. There is no single age cutoff; suitability is judged on symptoms, function, imaging, and overall health. For broader context on degenerative joint disease and its progression, see our Medical Conditions guide.
How the Procedure Is Performed
Most knee replacements take 60 to 120 minutes in the operating room. Anesthesia is typically a spinal or epidural block paired with sedation, although general anesthesia remains an option. Once you are positioned and the leg is prepped, the surgeon makes an incision over the front of the knee, moves the kneecap aside, and removes the damaged cartilage and a few millimeters of bone from the ends of the femur and tibia. Precision cutting guides, sometimes assisted by robotic or computer-navigation platforms, shape the bone to fit the implant.
The femoral component is metal, the tibial tray is metal with a polyethylene (medical-grade plastic) insert that acts as a smooth spacer, and the patella is often resurfaced with a plastic button. Components are either cemented in place or designed for biological bone ingrowth. The surgeon then closes the joint capsule, places a drain in some cases, and finishes with sutures or staples. Many hospitals now perform knee replacement as outpatient or 23-hour surgery, with discharge the same or next day, per Cleveland Clinic. Whether you go home the same day depends on your health, home support, and your surgeon’s protocol.
Partial vs. Total Knee Replacement
Not everyone needs the whole joint replaced. In a partial (unicompartmental) knee replacement, only the single worn compartment — most often the inner (medial) side — is resurfaced, sparing the healthy ligaments and cartilage in the rest of the knee. Candidates typically have arthritis confined to one compartment, reasonably preserved motion, and intact ligaments. Partial replacement generally means a smaller incision, less blood loss, and often a quicker early recovery.
A total knee replacement resurfaces all the affected surfaces and is the more common and more versatile option, especially when arthritis involves more than one compartment or the joint is deformed. Partial replacements can wear out or progress and later require conversion to a total replacement. Which approach fits you is a decision your surgeon makes based on your imaging, ligament health, alignment, and goals — it is not a choice to make from a checklist.
Preparation and What to Expect on the Day
Pre-surgery preparation usually starts four to six weeks out. Expect a medical clearance visit, blood work, an EKG if you are over 50 or have cardiac risk factors, and dental clearance to reduce infection risk. Many surgeons prescribe a “prehab” program of quadriceps and hip strengthening, since stronger muscles before surgery tend to shorten recovery. You will also be asked to stop certain blood thinners, NSAIDs, and supplements before the operation — but only on your surgeon’s specific instructions, since stopping some medications on your own can be dangerous.
On surgery day, plan for several hours at the hospital or surgery center even if you are going home that day. After the operation, a physical therapist will usually get you out of bed within hours, walking with a walker. Pain control combines a multimodal approach: acetaminophen, a short course of opioids when needed, NSAIDs if appropriate, and sometimes a peripheral nerve block. Many patients are surprised by how soon they bear weight, though early recovery is still uncomfortable and varies from person to person.
Recovery Timeline and Rehab
The first two weeks focus on swelling control, walking with an assistive device, and regaining range of motion. Outpatient or home physical therapy typically starts within a week. By about four to six weeks, most patients walk without a cane indoors, and per AAOS, driving generally returns around four to six weeks — once you are off opioid pain medication and can brake and react safely (often sooner for a left knee with an automatic transmission). Sleep is often disrupted for the first month because of position-dependent discomfort.
By three months, most patients are back to nearly all daily activities, and many are golfing, biking, or walking longer distances. Final recovery, including the resolution of stiffness and occasional warmth around the joint, can take 9 to 12 months. Range-of-motion gains taper after the first three months, so consistent rehab in those early weeks matters most. AAOS guidance recommends avoiding high-impact activities like running and singles tennis to help extend implant life, while encouraging low-impact activity such as walking, swimming, and cycling. Your own timeline may be faster or slower — follow the plan your surgeon and physical therapist set for you.
Risks, Complications, and Outcomes
Serious complications are uncommon but real, and knowing them helps you spot trouble early. According to AAOS and Mayo Clinic:
- Blood clots (venous thromboembolism): Deep vein thrombosis (DVT) is among the most common complications after knee replacement, and a clot that travels to the lungs (pulmonary embolism, or PE) can be life-threatening. Surgeons routinely use prevention — blood thinners, compression stockings or boots, and early walking — but clots can still occur.
- Infection: Occurs in fewer than 2% of patients and can develop days, weeks, or even years after surgery, sometimes seeded by dental work, urinary, or skin infections.
- Stiffness that occasionally requires a manipulation procedure.
- Other risks: nerve or blood-vessel injury, periprosthetic fracture, wound problems, and persistent pain of unclear origin (uncommon).
- Implant wear or loosening, which can eventually require revision surgery.
Outcomes are generally excellent: AAOS reports that more than 90% of modern total knee replacements are still functioning at 15 years, and most patients get durable pain relief and improved function.
⚠️ When to seek emergency care after knee replacement. Blood clots are one of the most serious post-operative risks. Call 911 or go to the nearest emergency room right away if you have:
- Sudden shortness of breath or chest pain, especially with a cough (possible pulmonary embolism) — this is a medical emergency.
- New or increasing calf pain, tenderness, warmth, redness, or swelling in the leg (possible deep vein thrombosis).
- Signs of infection: a fever above roughly 100–101°F, chills, spreading redness, or increasing drainage or pain at the incision.
- Heavy bleeding from the incision, or a fall with sudden inability to bear weight on the operated leg.
Do not wait to see whether these symptoms pass. Follow your surgeon’s specific prevention and warning-sign instructions, and never adjust prescribed blood thinners on your own.
Alternatives and When Surgery May Not Be Needed
Knee replacement is rarely an urgent decision, and several alternatives can buy years of function. Weight loss reduces joint loading substantially, since each pound lost takes several pounds of force off the knee with every step, per NIAMS. Physical therapy targeting hip and core strength helps offload the medial knee compartment. Corticosteroid injections offer weeks to months of relief, while hyaluronic acid injections have more variable evidence. For younger patients with isolated medial wear, a unicompartmental replacement or a high tibial osteotomy may be considered before a full TKA.
If your imaging shows arthritis but your function is still good, watchful waiting is reasonable. Some patients also benefit from meniscus surgery or a diagnostic knee arthroscopy when a mechanical symptom such as locking is present alongside arthritis — although arthroscopy is no longer recommended as a treatment for arthritis itself.
Cost Considerations
Costs vary widely and every figure below is an estimate; verify prices for your own situation. The total billed cost of a knee replacement in the United States typically ranges from about $30,000 to $70,000 without insurance, depending on geography, hospital system, and implant choice. Medicare’s payment is generally much lower because of negotiated rates. Out-of-pocket costs for insured patients commonly fall between about $1,500 and $5,000 after deductible and coinsurance, but your share depends on your specific plan. Bundled-payment programs, ambulatory surgery centers, and direct-to-employer contracts have lowered prices in some markets. Our healthcare costs guide covers strategies for shopping surgical pricing and using HSA dollars effectively.
Frequently Asked Questions
How long does a knee replacement last?
More than 90% of modern total knee replacements are still functioning at 15 years, according to AAOS. Younger and heavier patients tend to wear implants faster. Revision surgery is more complex than the primary procedure, which is one reason surgeons often weigh timing carefully in younger patients.
How painful is recovery from knee replacement?
Pain typically peaks in the first one to two weeks and then steadily improves. Multimodal pain control, including nerve blocks and non-opioid medications, has reduced opioid use compared with a decade ago. Many patients are off prescription pain medication by four to six weeks, though this varies. Follow your surgeon’s pain plan and do not exceed prescribed doses.
What are the warning signs of a blood clot after knee replacement?
Call 911 for sudden shortness of breath or chest pain, which can signal a pulmonary embolism. New calf pain, tenderness, warmth, or swelling can signal a deep vein thrombosis — contact your surgeon or seek urgent care immediately. Blood clots are among the most common serious complications, so take these symptoms seriously and follow your prescribed clot-prevention plan.
Can I kneel after a knee replacement?
Kneeling is generally safe but often uncomfortable because the soft tissue over the implant is thinner. Some patients kneel without issue over time, while others find it permanently awkward. Kneeling does not typically damage the implant, but ask your surgeon about your specific case.
How soon can I drive after surgery?
AAOS notes driving usually returns around four to six weeks after a right knee replacement, once you are off opioids and can perform an emergency stop safely. Left knee replacement patients with automatic transmissions often drive sooner. Confirm with your surgeon before getting behind the wheel.
Knee replacement resurfaces a worn joint with metal and plastic parts and is usually done for end-stage osteoarthritis after conservative care has failed. Partial replacement treats one compartment; total replacement is more common. Most patients walk with an aid within days, resume many activities by 3-6 weeks, and keep improving for several months, and over 90% of implants last 15+ years. The most important safety point: blood clots (DVT/PE) are among the most common serious risks — seek emergency care for sudden shortness of breath, chest pain, or new calf pain and swelling — along with infection and, rarely, implant problems. Costs vary widely, so verify estimates. This article is educational and not a substitute for professional medical advice; every decision and your recovery plan should be directed by your orthopedic surgeon.
The Bottom Line
A knee replacement is one of the most successful operations in modern medicine, but it is also a planned commitment that requires honest self-assessment. The right time to discuss surgery with an orthopedic surgeon is when knee pain has narrowed your life, conservative care has plateaued, and imaging matches your symptoms. Ask about implant choice, partial versus total replacement, discharge plans, expected hospital stay, clot-prevention protocol, and the surgeon’s annual volume. If you are also evaluating a hip replacement or comparing approaches with a shoulder replacement, the same questions apply: surgeon experience, infection rates, a clear clot-prevention strategy, and a defined rehab plan are what consistently predict good outcomes.
Sources
- American Academy of Orthopaedic Surgeons (AAOS), OrthoInfo — “Total Knee Replacement” and “Activities After Knee Replacement.”
- Mayo Clinic — Knee replacement (indications, procedure, complications).
- Cleveland Clinic — Knee replacement (outpatient/23-hour surgery and discharge).
- MedlinePlus, U.S. National Library of Medicine — Knee joint replacement.
- National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) — Osteoarthritis.