A Guide to Knee Replacement Surgery

Medically Reviewed By Daniel Wiznia, MD

Knee replacement surgery is a procedure to remove a damaged surface of the knee joint and resurface worn-out cartilage with new gliding surfaces. The goal of knee replacement is to restore pain-free range of motion and full knee function. A doctor may recommend knee replacement for severe knee joint damage from a knee injury or arthritis. Osteoarthritis, which is an age-related condition, is a common reason for knee replacement surgery. With knee replacement surgery, people can live more active lives free of chronic knee pain. 

It can take 4–12 months to completely recover from knee replacement surgery. Undergoing physical therapy and paying particular attention to preventing infections, blood clots, and falls are key to a smooth and successful recovery. 

Since the first knee replacement surgery in 1968, there have been significant advances in surgical techniques and material components. In a 2019 study, using data from 2000–2014, researchers estimated that roughly 1.2 million knee replacement surgeries will take place in 2025.

This article looks at knee replacement surgery, including the different types of knee replacement, what makes a person a candidate for knee replacement, and what is involved before, during, and after knee replacement surgery. 

What is knee replacement surgery?

Knee replacement surgery, or knee arthroplasty, is surgery to replace parts of the knee with a prosthesis or artificial parts. You may need knee replacement surgery if you have knee joint damage and severe knee pain that makes daily activities, such as walking or climbing stairs,


Doctors recommend knee replacement surgery for severe knee pain, typically only after Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source nonsurgical treatments have stopped helping relieve pain or aid everyday activities. 

Knee replacement is common, but orthopedic knee surgery comes with risks and potential complications. Consider getting a second opinion about your treatment choices, including nonsurgical options, before deciding on knee replacement.

What are the different types of knee replacement surgery?

Knee replacement involves resurfacing and replacing any or all parts of a knee.

A knee joint is made up of the upper shinbone (tibia), the kneecap (patella), and the lower thighbone (femur). These bones are covered with soft, lubricated cartilage that protects the bone end and allows them to glide and function well.

The type of injury or damage to the knee you have sustained, as well as your lifestyle and overall health status, help inform what type of knee replacement your surgeon recommends.

The three common types of knee replacements are:

  • Total knee replacement: This surgery involves replacing all three compartments of the knee.
  • Partial knee replacement: This surgery involves replacing only one part of the knee joint.
  • Revision knee replacement: This surgery involves removing a previously inserted prosthesis. This procedure may be necessary if the original replacement does not provide any benefit. It is a more complex surgery than an initial replacement. 

Types of partial knee replacement

The two types of partial knee replacement are:

  • Unicompartmental knee replacement: This removes only one side of the affected joint. When only one part of the knee has an issue, this may be an alternative to a total knee replacement.
  • Kneecap replacement, or patellofemoral arthroplasty: This replaces the damaged bone and cartilage under the kneecap.

Although partial replacements tend to provide quicker and easier recovery because they save healthy tissue and bone, they are not always the best option. This disadvantage of partial knee replacement is the possibility of needing additional surgery in the future. 

After beginning a partial knee replacement, your surgeon may also decide that a total knee replacement is a better option for you. Discuss these possibilities with your doctor before surgery.

Why is knee replacement surgery necessary?

Your doctor may recommend knee replacement for severe knee joint damage from:

  • Knee injuries: Injuries include fractures, torn cartilage, and damage to ligaments or tendons that result in irreversible joint damage. 
  • Osteoarthritis: This degenerative joint condition is age-related arthritis. It is basic wear and tear of the knee joint. The breakdown of cartilage and bones within the joint results in pain, stiffness, and swelling. It is the most common reason for a knee replacement.
  • Post-traumatic arthritis: This can occur after a serious injury.
  • Rheumatoid arthritis: This autoimmune condition causes chronic inflammation that can damage the joints. 
  • Septic arthritis: This type of arthritis is due to an infection in the joint space.

Your doctor may only consider a knee replacement if other treatment options that involve less risk of complications have been ineffective. 

Your personal risk of complications from knee replacement surgery depends on your age, knee anatomy, and overall health. Talk with your doctor about your risks, and ask if the benefits of surgery outweigh the risks.

Who performs knee replacement surgery?

An orthopedic surgeon Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source performs knee replacement. An orthopedic surgeon has specialized training in the surgical treatment of diseases and conditions of the bones and connective tissues. Some orthopedic surgeons further specialize in joint reconstruction and replacement or in knee surgery specifically. 

Experience is critically important when you are choosing a knee replacement surgeon. Ask your orthopedic surgeon about the types and volume of surgeries they have performed on a monthly basis over the past several years.

A physical therapist will also work with you through your knee replacement recovery. A physical therapist will provide guidance on exercises and stretches to help you to regain muscle strength, range of motion, and overall function.

What does knee replacement surgery involve?

Knee replacements take place in hospitals and orthopedic surgery centers. A knee replacement can be either an open procedure or a minimally invasive procedure

Type of surgeries and techniques

There are many approaches to knee replacement surgery. Your doctor will explain which procedure is best for you based on your diagnosis, age, medical history, general health, and possibly personal preference.

Open knee replacement surgery requires an 8- to 10-inch incision over your knee to expose the whole joint and place the knee implant. 

With minimally invasive knee replacement surgery, your surgeon makes a 4- to 6-inch incision instead.

Minimally invasive surgery generally entails a faster recovery time, less pain, and a lower risk of some complications, such as infection.  

In some cases, a doctor may decide after beginning a minimally invasive technique that open surgery is necessary to safely and most effectively complete your surgery. Your surgeon may also decide after beginning a partial knee replacement that a total knee replacement is a better option for you. Discuss these possibilities with your doctor before surgery.

Types of anesthetic

Depending on the specific procedure, your surgeon will perform knee replacement surgery using a general anesthetic, a regional anesthetic, or both. 

  • General anesthetic: General anesthetic is a combination of IV medications, which are administered through a vein, and gases that put you into a deep sleep. Under general anesthesia, you are not aware of the surgery and do not feel any pain. 
  • Regional anesthetic: Peripheral nerve block is a type of regional anesthetic. An anesthesiologist injects an anesthetic around certain nerves to numb a large area of the body. For knee surgery, a regional anesthetic may include a spinal block that numbs from the waist down or a femoral nerve block that numbs most of the leg. If you are not receiving a general anesthetic with the nerve block, you will most likely have a sedative to keep you relaxed and comfortable.

Some surgeons may combine a peripheral nerve block with a general anesthetic. The numbing effect from the nerve block provides pain relief after surgery.

Surgical procedure overview

While you are under anesthesia, the surgeon exposes the joint by making an incision along the front of the knee. Generally speaking, the actual knee replacement surgery has four steps:

  • Ready the bone for an implant: This involves removing damaged cartilage and bone.
  • Resurface the joint: This involves shaping, sizing, and possibly drilling the ends of the bones to fit the metal or ceramic implant and inserting the implants into the bone.
  • Resurface the undersurface of the kneecap: Whether or not this step happens depends on the condition of your kneecap.
  • Implant a spacer: A spacer is a plastic disc that replaces your cartilage. The surgeon will place the spacer between the top and bottom metal implants to allow them to glide over each other. 

After your procedure, you will stay in the recovery area until you are alert, breathing effectively, and have vital signs that are stable. A physical therapist may visit and have you safely get up and start walking shortly after surgery. 

You may be discharged to go home, to go to a rehabilitation center, or to stay overnight in the hospital. Speak with your surgeon before your procedure about what the likely plan will be for you.

What are the risks and potential complications of knee replacement surgery?

Knee replacement surgery involves risks and potential complications. In a few cases, complications may become serious and life threatening.  

The risks of knee replacement surgery include blood clots, infections, falls and injuries, and other complications related to knee implants. The following sections discuss these complications and what you can do to reduce your risks.

Blood clots 

After surgery, a blot clot can form in veins in the leg or pelvis. These can be life threatening if they break free and travel to your lungs.

Things you can do to prevent blood clots include:

  • wearing compression wraps when resting
  • walking frequently
  • taking blood thinner medication as prescribed

Know the symptoms of a potential blood clot and report any calf pain or redness or swelling in your lower leg.

Go to the nearest emergency room if you have shortness of breath, chest pain, or a racing heartbeat. These symptoms may indicate a pulmonary embolism, which is when a blood clot has moved to the lungs. 


An infection can occur at the incision wound or deep within the knee around the prosthesis. Your care team will provide detailed instructions on caring for your wound and tell you signs of infection to look for. These include:

  • increased pain and warmth around the wound
  • discharge or a bad smell around the wound
  • worsening redness or swelling in the surgical area that is not improving with ice therapy
  • new numbness or tingling
  • fever higher than 101ºF (38ºC) or chills 

You can reduce your risk of infection by:

  • following any instructions from your surgeon for cleansing your skin days before surgery
  • washing your hands frequently
  • keeping the incision wound clean and dry
  • contacting your dentist if you have toothaches or think you might have a tooth infection, as oral infections can enter the bloodstream and potentially infect the surgical site

Falls and injuries

After surgery and during recovery, you have an increased risk of falling. To prevent falls and injuries:

  • Use assistive devices, including a walker, crutches, and later a cane. Your physical therapist can show you how to correctly use these devices.
  • Remove rugs and other trip hazards around the house.
  • Get a stable chair with a firm seat, preferably one that has a high seat, as well as an ottoman or a bench to elevate your leg.  
  • Install a raised toilet seat with handles. Also, consider installing shower grab handles. 

Potential complications of knee replacement

Most knee replacements are successful, but potential complications of the implant include:

  • chronic knee pain, which is rare
  • dislocation of the new joint, which is also rare
  • loosening of the new joint, which may require additional surgery
  • nerve, muscle, or blood vessel damage
  • fluid buildup in the knee joint
  • decreased range of motion, typically from scarring
  • wear and tear of the new joint, which may eventually lead to needing another knee replacement surgery

You can reduce the risk of certain complications by carefully following your treatment and recovery plan.

How do I prepare for knee replacement surgery?

The steps you take before surgery can improve your comfort and outcome.

To prepare for a knee replacement:

  • Answer all questions your surgeon asks about your medical history, allergies, and medications.
  • Get preoperative testing as directed. Testing will vary depending on your age, health, and specific procedure and may include a chest X-ray, electrocardiogram, or blood tests.
  • If required, lose any excess weight before surgery by following a healthy diet and exercise plan.
  • Do not eat or drink before surgery as directed.
  • If applicable, stop smoking as soon as possible. Even quitting for just a few days can be beneficial and help the healing process.
  • Take or stop medications exactly as directed. Your doctor will explain when to stop taking aspirin, ibuprofen, blood thinner medication, and other medications and supplements.
  • Prepare your home for recovery by removing trip hazards, preparing a recovery place that includes a firm chair and an ottoman to elevate your leg, and renting a walker or cane.  

What can I expect after knee replacement surgery?

Knowing what to expect makes it easier to plan and prepare for a successful recovery.  

How long will it take to recover?

Recovery time varies depending on the procedure, the type of anesthetic your surgeon uses, your general health and age, and other factors. It will probably be several months before you feel back to being able to perform everyday activities. Full recovery and range of motion can take 4–12 months.

Physical therapy is an essential part of recovery. It begins very soon after surgery, even during hospitalization. Gradually, you will regain knee function with less pain.

Will I feel pain?

Your doctor will prescribe a course of pain medication as well as over-the-counter (OTC) pain relievers to help you feel comfortable, get the rest you need, and keep up with physical therapy

The key to pain control is to take your pain medications, both prescription and OTC, as your doctor prescribes or according to package directions. Staying ahead of the pain is important for healing and ensuring a smooth recovery.

What type of scar will I have?  

Surgical incisions leave scars, which form as new tissue develops and brings together the open parts of the wound. After knee replacement surgery, you will have one or more scars. Depending on the surgeon’s approach, scars can be along the front and toward the middle of the knee or alongside the knee. 

The length of the scar depends on the procedure. A minimally invasive knee replacement leaves a shorter scar, usually about 4–6 inches. An open procedure leaves a longer scar, usually about 8–10 inches.

How obvious a scar is depends on the surgery and several factors unique to you. For example, your age, skin tone, and even nutritional status can all affect how a scar forms.

If you are concerned about scars after your knee replacement surgery, ask your surgeon what steps, if any, you can take to minimize their appearance.

When should I call my doctor?

It is important to keep your follow-up appointments after a knee replacement. Contact your doctor for questions and concerns between appointments.

Call your doctor right away or seek immediate medical care if you have:

  • bleeding
  • breathing problems, such as shortness of breath, difficulty breathing, labored breathing, or wheezing
  • changes in alertness, such as unresponsiveness or confusion
  • chest pain, chest tightness, chest pressure, or palpitations
  • fever
    • A low grade fever (lower than 101°F or 38ºC) is common for a couple of days after surgery. It is not necessarily a sign of a surgical infection. However, you should follow your doctor’s specific instructions about when to call for a fever.
  • an inability to urinate or have a bowel movement
  • pain, redness, or swelling in the leg, especially in the calf, which may indicate a blood clot
  • numbness or tingling in the affected leg
  • pain that is not responding to your pain medication
  • swelling, redness, pus, or drainage affecting your incision site

Will I have limitations after a knee replacement?

In most cases, a knee replacement results in very few limitations or restrictions to your daily routine. You might even be able to enjoy activities that you had to stop before surgery. 

To extend the life of your knee implant, your doctor may recommend avoiding:

  • activities that could overload your knees, such as heavy lifting
  • contact sports and high impact activities, including jogging
  • sports that require you to move laterally, such as skiing or racquetball

Your doctor will discuss specific limitations with you. Keep in mind that any restrictions you have may ease with time as your leg strength improves.


Knee replacement surgery is a procedure to remove and replace damaged knee joint surfaces with metal or ceramic implants and new gliding surfaces. New three-dimensional printing technology is helping surgeons custom fit implants before surgery. A knee replacement can significantly improve your mobility, allowing you to lead an active life without knee pain.

Complete recovery can take 4–12 months. Undergoing physical therapy and taking steps to prevent infections, blood clots, and falls are key to a smooth recovery. 

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Medical Reviewer: Daniel Wiznia, MD
Last Review Date: 2022 Feb 28
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