Total knee arthroplasty
Original Editors - Lynn Wright
- 1 Definition/Description
- 2 Clinically Relevant Anatomy
- 3 Epidemiology /Etiology
- 4 Characteristics/Clinical Presentation
- 5 Diagnostic Procedures
- 6 Outcome Measures
- 7 Examination
- 8 Medical Management
- 9 Physical Therapy Management
- 10 References
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. The level of bone loss will dictate 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 AnatomyKnee 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. 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 the ligaments and are surrounded by a capsule.
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 . Osteoarthritis causes the cartilage of the joint to become damaged and no longer able to absorb shock. There are a lot of external risk factors that can cause knee osteoarthritis. For example: being overweight, previous knee injuries or partial removal of a meniscus,  rheumatoid arthritis, fractures and congenital factors. There might also be some genetic factors the contribute to the development of osteoarthritis, but more research is necessary. Total knee arthroplasty is more commonly performed on women and incidence increases with age.
Pain is the main complaint of patients' with degenerated knee joints. 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.
Stiffness is the most common complaint following primary total knee replacement, affecting approximately 6 to 7% of patients undergoing surgery. In addition to stiffness, the following complications can impact on function following this surgery:
- Loosening or fracture of the prosthesis components
- Joint instability and dislocation
- Component misalignment and breakdown
- Nerve damage
- Bone fracture (intra or post operatively)
- Swelling and joint pain
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. Patients co-morbidities also need to be considered Obesity is an important factor that needs to be considered prior to surgery as evidence suggests a correlation between higher body mass index (BMI) and poorer post-operative functional outcomes 
These are the different stages of osteoarthritis that you can see at a MRI.
- Knee disability and Osteoarthritis Outcome score (KOOS)
- The Timed Get Up and Go Test (TUG)
- Visual Analogue Scale (VAS)
- Range of motion (ROM) 
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
- 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. 
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, a polyethylene shock absorbing disc and sometimes a replacement patella. 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 size and shape is chosen on a patient by patient basis.
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.
Physical Therapy Management
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 immediately ready to practice a correct version of the appropriate exercises. It is also important that the functional status of the patient before surgery is optimised to assist recovery. The focus of a pre-operative training program should be on postural control, functional lower limb exercises and strengthening exercises for both of lower extremities.
Unfortunately, there is limited evidence to support that pre-operative physiotherapy brings significant improvements in patient outcome scores, lower limb strength, pain, range of movement or hospital length of stay following total knee arthroplasty.
Evidence indicates that physiotherapy is always beneficial to the patient post-operatively following total knee arthroplasty. Although specificity of intervention can vary, the benefits of the patient actively participating and moving under physiotherapists' direction are clear and supported by the evidence. There is also some low-level evidence that accelerated physiotherapy regimens can reduce acute hospital length of stay.
Perhaps the most important role of physiotherapists in the management of patients following TKA is facilitating mobilisation within 48 hours of surgery, sometimes as early as the same day as the operation (Day 0). The optimal physical therapy protocol should also include strengthening and intensive functional exercises given through land-based or aquatic programs, that are progressed as the patient meets clinical and strength milestones. Due to the highly individualized characteristics of these exercises the therapy should be under supervision of of a trained physical therapist for best results.  
There is evidence that cryotherapy improves knee range of motion and pain in the short-term. With are relatively small sample size of low quality evidence, it is difﬁcult to draw solid conclusions regarding the outcomes measured and speciﬁc recommendations cannot be made about the use of cryotherapy.” 
Common bed and chair exercises
- Ankle plantarflexion/dorsiflexion
- Isometric knee extension in outer range
- Inner Range Quadriceps strengthening using a pillow or rolled towel behind the knee
- Knee and hip flexion/extension
- Isometric buttock contraction
- Hip abduction/adduction
- Straight leg raises
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