Total Knee Arthroplasty

Original Editors - Lynn Wright

Top Contributors - Safiya Naz, Loes Verspecht, Kim Jackson, Lucinda hampton, Kun Man Li, Jess Bell, Ellen Wynant, Lisa Ingenito, Claire Knott, George Prudden, Karolien Van Melkebeke, Lynn Wright, Tarina van der Stockt, Lauren Lopez, Famke Coosemans, Leana Louw, 127.0.0.1, Evan Thomas, Ewa Jaraczewska, Greg Walding, Daniele Barilla, WikiSysop and Karen Wilson

Definition/Description

Total knee arthoplasty (TKA) or total knee replacement (TKR) is a orthopaedic surgical procedure where the articular surfaces of the knee, the femoral condyles and tibial plateau, are replaced. There is at least one polyethylene piece, placed between the tibia and the femur, as a shock absorber. In 50% of the cases the patella is also replaced. Reasons for a patella replacement are osteolysis, maltracking of the patella, failure of the implant,... The aim of the patella reconstruction is to restore the extensor mechanism. It depends on the level of bone loss, which kind of patella prosthesis is placed. The main clinical reason for the operation is osteoarthritis with the goal of reducing an individuals pain and increasing function..

Clinically Relevant Anatomy

The Knee is a modified hinge joint, allowing motion through flexion and extension, but also a slight amount of internal and external rotation. There are three bones that form the knee joint: the upper part of the Tibia , the lower part of the femur and the patella. The bones are covered with a thin layer of cartilage, which ensures that friction is limited between the bones. On both the lateral and medial sides of the knee, there is a meniscus, which adheres the tibia to the femur, but is also a shock absorber. The three bones are kept together by ligaments and are surrounded by a capsule.

Epidemiology /Etiology

When all the compartments of the knee are damaged, a total knee prosthesis may be necessary. The main cause of need for a total knee prosthesis is Osteoarthritis. (evidence level: 1b)  Because of the presence of osteoarthritis, the cartilage of the joint becomes damaged and is no longer able to absorb shocks. There are a lot of external risk factors that can cause knee osteoarthritis. For example: overweight, previous knee injuries, the (partial) removal of a meniscus,...   (evidence level: 2a) Other causes are rheumatoid arthritis, fractures and congenital factors. There might also be some genetic factors in the development of osteoarthritis, but more research is necessary. (evidence level: 2b)
Total knee arthroplasty is mostly performed on women and increases with age.

Characteristics/Clinical Presentation

Pain is the main complaint of persons with a degenerated knee joint At first pain is felt only after rest periods; this is also called ‘starting pain’; after a couple of minutes the pain slowly fades away. When the knee joint degeneration increases, the pain can also occur during rest periods, and it can affect sleep at night. Individuals' can also complain of knee stiffness and crepitus. Due to pain and stiffness, function can decline and is manifests as reduced exercise tolerance, difficulty climbing stairs or slopes, reduced gait speed and increased risk of falls.

Post-operative complaints

Stiffness is the most prevalent early local complication of primary total knee replacement, affecting approximately 6 to 7% of patients undergoing surgery.

Complications

• Loosening or fracture of the prosthesis components
• Joint instability and dislocation
• Infection
• Component misalignment and breakdown
• Nerve damage
• Bone fracture
• Swelling and joint pain

Diagnostic Procedures

In order to assess the gravity of wear or injury the orthopedic surgeon carries out external tests, and the patient is likely to undergo imaging.

A prosthesis is a device often placed in people with osteoarthritis. Some signs and symptoms are significant for this group of patients who, most commonly, are women, in their fourth and fifth decades of life, with polyarthritis.

Patients co-morbidities also need to be considered (evidence level: 1b)

Obesity is also a factor we need to keep in mind, so the best thing to do is to encourage the patient to do something about his or her weight prior to surgery. This will be important for a better and faster recovery. (evidence level: 1b)

These are the different stages of osteoarthritis that you can see at a MRI.

Outcome Measures

• Knee disability and Osteoarthritis Outcome score (KOOS)
• The Timed Get Up and Go Test (TUG)
• Visual Analogue Scale (VAS)

Examination

Pre-operative tests

First the examiner should ask the patient about the history of complaints and also about expectations from surgery. The examiner should then perform a full objective examination. After this different tests could be carried out to determine whether the patient needs total knee arthroplasty:

• Active ROM
• Passive ROM
• Muscle power
• Functional tasks

Post-operative tests

• Inspection: of the wound/scar, redness, adhesion of the skin. When infection of the wound is suspected the patient must be referred to an orthopedist or an emergency doctor.

• Palpation: post-operative swelling, hypertonia (adductors), pain and warmth.

Medical Management

The purpose of the surgical procedure is to achieve pain free movement again, with full functionality of the joint, and to recreate a stable joint with a full range of motion.

Total knee arthroplasty is chosen when the patient has serious complaints and functional limitations. Surgery takes some 60-90 minutes and involves putting into place a three-part prosthesis: a part for the femur, a part for the tibia and a part for the patella (not always) and a polyethylene joint. A high comfort insert design is chosen to achieve this. The perfect prosthesis doesn’t exist; every prosthesis must be different and the most appropriate chosen for each patient.

During surgery a tourniquet is sometimes used; this will ensure that that there is less blood loss. However, when a tourniquet is not used, there will be less swelling and less pain. (evidence level: 1b)

Physical Therapy Management

Pre-operation

The physical therapist can choose to teach the patient the exercises before surgery in order that the patient might understand the procedures and, after surgery, be ready to practice a correct version of the appropriate exercises. In this way recovery can begin very rapidly. It is also important that the functional status of the patient before surgery be as good as possible. This will help recovery after surgery. Furthermore the patient can also start a training program before surgery. The patient has to train his postural control, needs to perform functional exercises and develop the strength of the lower extremities. (evidence level: 1b)

Post-operation

In several studies the effect of physiotherapy after total knee arthroplasty was examined. Generally these studies have shown that physiotherapy is always beneficial. The reports are not always clear regarding the kind of physiotherapy practiced, but all stress the importance of the patient moving. For example aqua therapy, balance training or cycling were added to the basic therapy, but there was no difference between the results obtained by the various therapies. One study compared a group of patients who didn't receive physiotherapy and a group who did. In this study it was clear that physiotherapy actually has its benefits. (evidence level: 1a)

There are four steps in the revalidation process. The first step is mobilizations, then static strength, followed by dynamic strength, and ending with stabilization. The mobilizations and static strength training can be started at almost the same time. The first day after surgery it is important to stimulate blood circulation. Therefore the patient can be asked to perform a flexion and extension with the feed.

Already from day 2, one can start to walk with the patient with an ambulator or walker. The therapist also starts mobilization exercises regarding flexion and extension; usually these exercises are performed on a shuttle bench. The flexion and extension of the knee can also be immediately practiced actively .

Common bed and chair exercises

• Ankle plantarflexion/dorsiflexion
• Isometric knee extension in outer range
• Knee extension/flexion using a pillow behind the knee
• Knee and hip flexion/extension
• Isometric buttock contraction
• Hip abduction/adduction
• Straight leg raise

Clinical Bottom Line

The knee prosthesis is the most commonly placed prosthesis in the human body, the main cause is general wear and degeneration of the joint. There are several risk factors, such as obesity, that we have to keep in mind, and cannot underestimate, in this degeneration process with loss of stability and other structural and functional problems.