TKA stands for total knee arthroplasty, the medical term for total knee replacement surgery. It’s one of the most common orthopedic procedures performed worldwide, designed to relieve chronic knee pain and restore mobility when the joint has deteriorated beyond what medications or physical therapy can manage.
What the Procedure Involves
During a TKA, a surgeon removes the damaged surfaces of the knee joint and replaces them with artificial components made of metal alloys and a durable plastic spacer. The procedure resurfaces three areas: the bottom end of the thighbone (femur), the top of the shinbone (tibia), and often the underside of the kneecap (patella). These components are typically secured with bone cement, and the plastic spacer sits between the metal parts to create a smooth, low-friction gliding surface that mimics a healthy knee.
The surgery usually takes one to two hours under general or spinal anesthesia. Surgeons make an incision over the front of the knee, move the kneecap aside, and carefully reshape the bone ends using precise cutting guides before fitting the implants. The plastic spacer can be adjusted in thickness to ensure the knee feels stable and balanced when it bends and straightens.
Why TKA Is Performed
Osteoarthritis is by far the most common reason people need a total knee replacement. Years of wear gradually erode the cartilage cushioning the joint until bone grinds against bone, causing pain, stiffness, and difficulty with everyday activities like climbing stairs or walking across a parking lot. Rheumatoid arthritis and post-traumatic arthritis (damage from an old injury) are less common but equally valid reasons.
Surgery is typically recommended after non-surgical treatments have stopped providing adequate relief. That includes anti-inflammatory medications, corticosteroid injections, bracing, weight management, and physical therapy. There’s no strict age cutoff; surgeons base the decision on how much the knee pain limits your daily life rather than on a number.
Partial vs. Total Knee Replacement
Not every damaged knee needs a full replacement. When arthritis affects only one side of the joint, a partial knee replacement (unicompartmental knee arthroplasty, or UKA) replaces just that compartment. Compared to TKA, partial replacement involves a smaller incision, less bone removal, shorter hospital stays, less blood loss, and faster initial recovery. Patients who receive a partial replacement also tend to have greater range of motion at discharge and a higher activity level early on.
The trade-off is narrower eligibility. You generally need to have intact ligaments, arthritis confined to a single compartment, no significant deformity, and less than about 10 degrees of stiffness when straightening the knee. When arthritis is widespread across the joint, TKA is the more reliable option. At five years, survival rates for both implant types are comparable.
How Long Implants Last
Modern knee replacements are remarkably durable. A long-term follow-up study of cemented implants found survival rates of 93.5% at 10 years, 91.7% at 15 years, and 90.8% at 20 years when counting revisions for any reason. When looking only at revisions caused by the implant loosening from the bone, the most common mechanical failure, survival climbed to 99% at 15 years and 98% at 20 years. Most people who receive a TKA in their 60s or 70s can expect the implant to last the rest of their lives.
Recovery Timeline
Recovery from TKA follows a predictable arc, though individual timelines vary based on fitness, age, and how closely you follow your rehabilitation program.
- First week: The priority is managing pain and swelling, protecting the incision, and beginning gentle quadriceps activation. Most patients start walking with a walker or crutches within a day of surgery.
- Weeks 1 through 4: Physical therapy focuses on restoring full straightening of the knee (extension) and bending it past 90 degrees. You’ll start building strength in the thigh muscles and reducing your reliance on assistive devices.
- Weeks 4 through 8: Bending typically progresses past 110 degrees. Gait training helps you walk more naturally, and balance exercises become part of the routine. Many people transition from a walker to a cane during this phase.
- Weeks 8 through 12: The goal is reaching at least 80% of the strength in your non-surgical leg and achieving enough range of motion (around 120 degrees or more) to handle daily tasks comfortably, including getting in and out of a car, navigating stairs, and sitting in low chairs.
- Months 3 through 6: Strength and endurance continue to improve. Low-impact activities like golf, doubles tennis, hiking, and swimming are gradually reintroduced with your surgeon’s clearance.
Most people notice the biggest improvements in the first three months, though continued gains in strength and confidence can stretch out to a full year.
Risks and Complications
TKA is considered safe, but like any major surgery it carries risks. Blood clots are the most closely monitored concern. Deep vein thrombosis (a clot in the leg veins) occurs in roughly 9% of TKA patients in large cohort data, and pulmonary embolism (a clot traveling to the lungs) is rarer but more dangerous. Surgeons prescribe blood thinners and encourage early walking specifically to reduce this risk.
Infection at the surgical site occurs in a small percentage of cases but can be serious because bacteria on an artificial joint are difficult to clear. Signs include increasing redness, warmth, swelling, or drainage from the incision, especially with fever. Stiffness that doesn’t improve with therapy, instability, and nerve or blood vessel injury round out the less common complications. Choosing an experienced surgical team and following your rehabilitation plan closely are the two most practical things you can do to lower your risk.
Robotic-Assisted TKA
A growing number of surgeons use robotic-assisted systems to perform TKA. These platforms create a 3D model of your knee before surgery and guide the saw cuts in real time, allowing more precise alignment of the implant. Studies confirm that robotic-assisted TKA reduces alignment errors by about two-thirds compared to conventional technique, with less than one degree of average deviation from the target.
That precision, however, hasn’t yet translated into dramatically different functional outcomes for patients. Pain and function scores at follow-up are similar between robotic and conventional approaches, and range of motion after surgery is essentially the same. Robotic cases do take roughly 20 minutes longer in the operating room. The technology is still evolving, and whether the improved alignment leads to better implant longevity over 15 to 20 years remains an open question.