Knee Arthroplasty

Knee replacement, Total knee replacement, Total knee arthroplasty, TKA, Partial knee replacement

Knee arthroplasty is one of the most successful surgeries performed today, helping people with severe knee pain and limited mobility return to their daily activities and enjoy life again.

Table of contents

• What is knee arthroplasty?
• Understanding the knee
• Conditions treated with knee arthroplasty
• Types of knee arthroplasty
• How the surgery is performed
• Preparing for surgery
• Recovery and rehabilitation
• Benefits and success rates
• Risks and complications
• How long does a knee replacement last?
• Life after knee arthroplasty

What is knee arthroplasty?

Knee arthroplasty, also known as knee replacement, is surgery to replace parts of an injured or worn-out knee joint^[1]. During the surgery, damaged bone and cartilage (the smooth tissue that covers and protects bones where they meet) are replaced with parts made of metal and plastic^[1]. These artificial parts are called a prosthesis^[1].

This surgery is one of the most highly effective, cost-efficient, and consistently successful procedures in orthopedics^[4]. It can help ease pain and make the knee work better, allowing people to return to normal activities^[1]. Surgeons in the United States perform more than 850,000 knee replacements each year^[3], with some sources reporting over 700,000 annually^[2].

Understanding the knee

• Femur (thighbone)
• Tibia (shinbone)
• Patella (kneecap)

The knee is the largest joint in the body and is essential for performing most everyday activities^[2]. It is made up of three main bones: the lower end of the femur (thighbone), the upper end of the tibia (shinbone), and the patella (kneecap)^[2].

The ends of these three bones are covered with articular cartilage, a smooth substance that protects the bones and enables them to move easily within the joint^[2]. Between the femur and tibia are C-shaped wedges called menisci, which act as shock absorbers that cushion the joint^[2]. Large ligaments hold the bones together and provide stability, while the long thigh muscles give the knee strength^[2].

All remaining surfaces of the knee are covered by a thin lining called the synovial membrane, which releases a fluid that lubricates the cartilage^[2]. In a healthy knee, all of these components work together to ensure smooth, natural movement. However, disease or injury can disrupt this harmony, resulting in pain, muscle weakness, and reduced function^[2].

Conditions treated with knee arthroplasty

A healthcare provider might recommend knee replacement if you have severe symptoms that don’t get better after trying nonsurgical treatments^[3]. These symptoms include joint pain, stiffness, limited mobility (trouble moving your knee), and swelling^[3].

Arthritis is the most common condition that causes people to need knee replacement surgery^[3]. Although there are many types of arthritis, most knee pain requiring replacement is caused by just three types^[2]:

• Osteoarthritis: This is an age-related, wear-and-tear type of arthritis where the knee cartilage wears away and the surface of the knee becomes pitted, eroded, and uneven^[1][2]. This is sometimes referred to as “bone-on-bone” arthritis, causing pain, stiffness, instability and a change in body alignment^[6]. Most people who choose to have a knee replacement have osteoarthritis^[3].
• Rheumatoid arthritis: Some people with rheumatoid arthritis may also need knee replacement^[3].
• Post-traumatic arthritis: This type of arthritis develops after a bone fracture in the knee caused by a car accident, fall, or sports injury^[3].

People who need knee replacement surgery often have problems walking, climbing stairs, and getting up out of chairs^[1]. Some may even begin to feel pain while sitting or lying down^[2]. The surgery is typically considered when nonsurgical treatments like medications, physical therapy, injections, and walking supports are no longer helpful^[2][4].

Types of knee arthroplasty

Your surgeon will recommend either a total or partial knee replacement based on the extent of damage to your knee joint^[3]:

Total knee replacement is the most common type of knee replacement^[3]. In this procedure, your surgeon will replace all three areas of your knee joint: the inside (medial), outside (lateral), and under your kneecap (patellofemoral)^[3]. If the entire joint needs to be replaced, the ends of the thighbone and shinbone are reshaped, and the entire joint is resurfaced^[1].

Partial knee replacement is when your surgeon only replaces some areas of your knee joint, usually if only one or two areas are damaged^[3]. If only one part of the knee is damaged, surgeons often can replace just that part^[1]. Partial knee replacements are more common in younger adults who have experienced an injury or trauma^[3].

How the surgery is performed

To decide whether a knee replacement is right for you, a surgeon checks your knee’s range of motion, stability, and strength^[1]. X-rays help show the extent of damage, and you might also need magnetic resonance imaging (MRI) or a computed tomography (CT) scan^[3]. The right artificial joints and surgical techniques needed depend on many factors including age, weight, activity level, knee size and shape, and overall health^[1].

On the day of your surgery, you’ll receive anesthesia to numb your body and make sure you don’t feel any pain^[3]. An anesthesiologist will give you either general anesthesia to put you to sleep during your surgery or a regional anesthesia (such as spinal anesthesia) to numb you from the waist down^[3][6].

During a total knee replacement, the surgeon makes an incision (cut) in the knee and moves the patella (kneecap) to the side^[6]. If any bone spurs (small bony growths) are present, they will be removed^[6]. Next, the two menisci between the femur and tibia are removed, along with the anterior cruciate ligament (ACL) and, in some cases, the posterior cruciate ligament (PCL)^[6].

During the main phase of the operation, your surgeon will remove damaged cartilage and bone, then insert the prosthetic knee joint^[3]. The surgeon cuts and removes cartilage and some bone from the upper part of the tibia and lower sections of the femur^[6]. The tibia and femur are then capped with metal implants to create new surfaces for the joint^[6]. A plastic spacer is inserted that recreates the smooth cushion of your cartilage that was damaged or removed^[3]. If the kneecap has also degraded, the surface on its underside may be cut away and replaced with a plastic implant^[6].

The artificial knee joint has metal caps to resurface the thighbone and shinbone, and high-density plastic to replace damaged cartilage^[1]. The implants used in knee replacement are smooth like the surfaces of a healthy knee^[6]. Finally, the various layers of tissue are repaired with dissolvable sutures and the skin incision is closed with sutures or surgical staples^[6].

Preparing for surgery

Your healthcare provider and surgeon will tell you what you need to do to get ready for surgery^[3]. In general, you’ll need:

• A physical exam to make sure you’re healthy enough for surgery^[3]
• Blood tests^[3]
• An electrocardiogram to check your heart health^[3]
• A dental exam to reduce your risk of developing an infection after surgery^[3]
• Imaging tests, including a knee X-ray^[3]

Tell your provider and surgeon about any medications and over-the-counter supplements you take, as you may have to stop taking some medications or supplements before your surgery^[3]. Your surgeon will tell you when you should stop eating and drinking the day before your surgery. Most people need to avoid eating and drinking 12 hours before their surgery^[3].

Recovery and rehabilitation

Some people go home the same day they have surgery, while others will stay in the hospital a few days^[1]. The majority of patients spend one night in the hospital, though occasionally someone needs to stay a little longer, especially if they live in a walk-up or don’t have a lot of family support^[14].

One of the goals after surgery is to get patients out of bed as soon as the anesthesia wears off^[14]. Your care team will get you up and walking within a few hours after your knee replacement surgery^[3]. Physical therapists and nurses will make sure that you can safely get out of bed, transfer from your bed to a chair, and get to the bathroom^[14]. They will also ensure that you have enough range of motion in your new knee to begin walking with a walker right away^[14].

To help prevent blood clots, you’ll most likely take blood thinners and wear special socks or coverings on your legs for a short time after surgery^[5]. Physical therapy is an important part of recovery and starts from the first time you get out of bed^[14]. While you are still in the hospital, your physical therapist will check your range of motion, or how much you can bend and straighten your leg^[14].

After you leave the hospital, a physical therapist may come to your home for the first few weeks^[14]. They will work on maintaining the range of motion in your knee and helping you rebuild strength in the surrounding muscles. Eventually, you will transition to getting physical therapy at a clinic or other facility^[14]. It is important to do these exercises regularly^[5].

Recovery from total knee replacement is gradual, typically taking three to six months for most patients to regain strength, mobility and return to daily activities^[13]. Some improvement can continue for up to a year^[13]. Most people who follow their recovery instructions can get back to nearly all of their normal daily activities within 3 to 6 weeks after surgery^[5]. You may need to use a cane or walker for several weeks after the surgery, and it will probably also be several weeks before you can drive^[5].

It can take up to a year to recover fully after a knee replacement, but you’ll be able to resume some of your usual activities gradually as you heal^[3]. The success of your surgery depends a lot on what you do at home to help yourself recover^[5].

Benefits and success rates

Knee replacement is one of the most successful orthopedic surgeries performed today^[6]. Most patients experience reduced or eliminated knee pain, increased ability to move and an overall improvement in quality of life^[6].

Total knee replacement is one of the most successful procedures in all of medicine^[2]. After recovering from surgery, most people can move better with less pain than before surgery^[5]. The surgery provides reliable outcomes for patients suffering from end-stage degenerative knee osteoarthritis, which is characterized by severe joint pain, stiffness, and reduced mobility^[4].

The surgery aims to alleviate these symptoms and restore function by replacing the damaged knee joint with prosthetic components, resulting in improved pain relief and enhanced overall well-being for patients^[4].

Risks and complications

The chance of having problems after knee replacement surgery is low, but there are risks after any surgery^[5]. Possible problems after knee replacement surgery include:

• Infection^[5]
• Blood clots^[5]
• Heart attack^[5]
• Stroke^[5]
• Nerve damage^[5]
• Scarring that limits how far you can bend your knee^[5]

Your age, general health, and how active you are can all affect your risk of having a problem after knee replacement surgery^[5].

How long does a knee replacement last?

A knee replacement doesn’t last forever^[5]. An implant can last from 15 to 25 years^[19]. If you’re under 60, you’re probably facing a revision (or do-over), but the most common revision is usually just an exchange of the plastic insert, which means most of the original implant stays, and the surgeon won’t necessarily need to remove more bone^[19].

Life after knee arthroplasty

After recovering from surgery, most people can move better with less pain than before surgery^[5]. However, having an artificial knee is not the same as having a normal, healthy knee^[5]. You need to protect your new knee by:

• Staying at a healthy weight^[5]
• Getting regular physical activity^[5]
• Not doing any high-impact activities, such as jogging, running, and jumping^[5]. Instead, you can try low-impact activities that are good for your knee, such as walking, biking, and swimming^[5]

Following knee replacement surgery, overexertion, skipping physiotherapy sessions, neglecting wound care or persistent pain, and ignoring medical advice should be avoided^[16]. Patients should focus on gradual recovery with regular gentle exercise, proper rest, wound care, and following professional guidance for the best chance of a full recovery^[16].

For the first few weeks after surgery, you need to take it easy, but you can return to most daily activities soon^[17]. After a few weeks, you can likely return to typical activities like driving, work, and household chores. However, it can take several months before you feel fully recovered^[17].