Total Knee Replacement

Question 1

Definition

Answer 1

• Aka is total knee replacement
  
  • Common orthopaedic surgery that involves replacing the articular surfaces (femoral condyles and tibial plateau) of the knee joint with smooth metal and highly cross-linked polyethylene plastic.
  • Aims to improve the quality of life of individuals with end-stage OA by reducing pain and increasing function.
  • Was found to improve patient’s sports and physical activity.
  • During surgery, there is at least one polyethylene piece, placed between the tibia and femur as a shock absorber.
  • The prostheses are usually reinforced with cement, but may be left uncemented where bone growth is relied upon to reinforce the components.
  • The patella may be replaced or resurfaced. Patella reconstruction aims to restore the extensor mechanism.
  • A quadriceps-splitting or quadriceps-sparing approach may be used.
  • The cruciate ligaments may be excised or preserved.
  • There are different types of surgical approaches, designs, and fixations.

Question 2

Clinically relevant anatomy

Answer 2

• The knee is a modified hinge joint that allows flexion and extension motions, with slight amounts of internal and external rotation.
  
  • Three bones form the knee joint: the upper part of the tibia, the lower part of the femur, and the patella.
  • The articular surfaces are covered with a thin layer of cartilage.
  • Menisci adhere to the lateral and medial surfaces of the tibial plateau and aids in shock absorption.
  • The knee joint is reinforced by ligaments and a joint capsule.

Question 3

Epidemiology / Aetiology

Answer 3

• The most common indication for a primary knee replacement is OA.
  
  • OA causes the cartilage of the joint to become damaged and no longer able to absord shock.
  • Risk factors for knee OA include gender, increased body mass index, history of a knee injury, and comorbidities.
  • Pain is typically the main complaint of knee OA.
  • Pain is subjective, and involves peripheral and central neural mechanisms that are modulated by neurochemical, environmental, psychological, and genetic factors.
  • TKR is more commonly performed on women and individuals of older ages.
  • Majority of TKR are performed on women.
  • Dramatic increases in TKR surgeries are projected to occur with an increasing rate of younger TKR recipients under the age of 60.
    Younger people undergoing TKR for knee OA are more likely to have morbid obesity, smoke, and their expected outcome is to return to vigorous activities, like sport.

Question 4

Diagnostic Procedures

Answer 4

• Before surgery, a full medical evaluation is performed to determine risks and suitability.
  
  • As part of this evaluation, imaging is used to assess the severity of joint degeneration and screen for other joint abnormalities.
    A knee radiograph is performed to check for prosthetic alignment before the closure of the surgical incision.

Question 5

Pre-surgical physiotherapy

Answer 5

• Post-surgical rehab exercises may be taught before surgery, so that patients may perform the appropriate exercises more effectively immediately after surgery.
  
  • A pre-surgical training programme may also be used to optimise the functional status of patients to improve post-surgical recovery.
  • Should focus on postural control, functional lower limb exercises, and bilateral lower limb strengthening exercises.
    Evidence supporting the efficacy of pre-surgical physiotherapy on patient outcome scores, lower limb strength, pain, range of movement or hospital length of stay following TKR is lacking.

Question 6

Post-TKA Surgery

Answer 6

• Surgery lasts 1-2 hours.
  
  • Majority of individuals begin physio during their inpatient stay, within 24 hours of surgery.
  • Range of motion and strengthening exercises, cryotherapy, and gait training are typically initiated, and a home exercise programme is prescribed before discharge from hospital.
  • There is low-level evidence that accelerated physiotherapy regimens reduce the length of stay in an acute hospital.
  • Patients are usually discharged after a few days stay in hospital and receive follow-up physiotherapy, in the outpatient or home care setting, within 1 week of discharge.

Question 7

Post-surgical physiotherapy

Answer 7

• Physiotherapy interventions are effective tools for improving patient’s physical function, range of motion, and pain in a short-term follow-up following TKR.
  Long term benefit and cost-effectiveness of physiotherapy interventions after TKR needs further study.

Question 8

Subjective Assessment

Answer 8

• Operative and post-operative complications, if any
  
  • History of knee and other MSK complaints
  • Past medical history and relevant comorbidities
  • Social factors and home set-up
  • Progress in-home exercises post-TKR surgery
  • Pain and other symptoms / discomfort (e.g., numbness, swelling)
  • Expectations from surgery and rehab
    Specific functional goals

Question 9

Objective Assessment

Answer 9

• Crucial to comprehensively evaluate various factors that contribute to patients recovery.
  
  • Observation of surgical wound or scar
  • Check for signs of infection (redness, dicharge (pus/odor), adhesions of the skin, abnormal warmth and swelling, expanding redness beyond the edges of the surgical incision, fever or chills). Suspicion of infection warrants medical referral
  • Knee swelling (circumference measurement)
  • Vital signs and relevant laboratory findings
  • Check for deep vein thrombosis
  • Palpation (for increased warmth and swelling
  • Assessment of muscle function and tone (for muscle activations e.g., quadriceps, vastus medialis oblqiue). Assessing hypertonia, particularly in the hip adductors. Impact on rehab: influences gait pattern and postural stability. May lead to altered gait, increasing stress on knee joint. Essential to address for comprehensive rehab.
  • Lower limb range of motion: active and passive knee range of motion in supine or semi-reclined position
  • Lower limb muscle activation and strength
    Gait. Timed up and go or 10 metre walk test may be used (depending on individuals ability and tolerance). Assess for guarding in knee flexion, avoidance to weight bear on the operative leg, antalgic patterns, etc.

Question 10

Outcome Measures

Answer 10

• Knee disability and osteoarthritis outcome score (KOOS)
  
  • Oxford Knee Score
  • Patient satisfaction
  • Walking tests - Timed Up And Go, 6 Minute Walk Test
  • Visual Analogue Scale (C=VAS)
  • Knee range of motion
    Western Ontario and McMaster Universities Osteoarthritis Index Score (WOMAC)

Question 11

Phase 1: up to 2-3 weeks post-surgery

Answer 11

• Patient education - pain science, pain management, the importance of home exercises, setting rehabilitation goals, and expectations
  
  • Achieve active and passive knee flexion to 90degrees, and full knee extension
    ○ Keep passive knee flexion range of motion testing to less than 90degreesin the first 2 weeks to protect surgical incision and respect tissue healing
  • Aim to achieve minimal pain and swelling
  • Achieve full weight bearing
  • Aim for independence in mobility and activities of daily living
  • During the early phase of rehab, it is important to establish a therapeutic alliance and provide education on pain management strategies.
  • Pain education may include appropriate usage of pain medication, cryotherapy, and elevation of the operated limb.
  • There is evidence that cryotherapy improve knee range of motion and pain in the short-term.
  • Icing after exercise may be helpful, but low quality evidence makes specific recommendations for the use of cryotherapy difficult.
  • Patients should be informed to avoid resting with a pillow under the knee as this may lead to contractures.
  • Important to review the patient’s home exercise program during the first physiotherapy session as home exercises are a critical component of recovery.
  • Post-surgical exercises given by surgeon and inpatient physio should be reviewed.
  • In the early phase, patients can be taught to use the stairs with their non-operated leg leading on the ascent, and their operated leg leading on the descent.
    E.g., exercises = ankle plantarflexion/dorsiflexion, inner range quads strengthening using a pillow or rolled towel behind the knee, isometric knee extension in the outer range, knee and hip flexion/extension, straight leg raises, isometric buttock contraction, hip abduction/adduction, bridging.

Question 12

Phase 2: 4-6 weeks post-surgery

Answer 12

• Aim to have no quadriceps lag, with good, voluntary quadriceps muscle control
  
  • Achieve 105 degrees active knee flexion range of motion
  • Achieve full knee extension
  • Aim for minimal to no pain and swelling
  • Physiotherapy sessions may be schedules one to times weekly.
  • Frequency may increase or decrease depending on individuals progress.
  • Achieving full knee extension is essential for functional tasks such as walking and stair climbing.
  • Knee flexion range of motion is required for comfortable walking (65 degrees), stair climbing (85degrees), sitting and standing (95degrees).
    In this phase, tissue mobilisation techniques may be used to improve scar mobility.

Question 13

Phase 3: 6-8 weeks post-surgery

Answer 13

• Strengthening exercises to ensure hypertrophy beyond neural adaptation
  
  • Lower limb functional exercises
  • Balance and proprioception training
  • While primary TKA has been reported to reduce falls incidence and improve balance-related functions such as single limb standing balance, the sub-optimal recovery of proprioception, sensory orientation, postural control, and strength of the operated limb post-TKA is well documented.
  • Literature highlights the importance of proprioceptive training, and pre-operative training that involves the non-operated limb.
  • Balance exercises may include single leg balancing, stepping over objects, lateral step-ups, and standing on uneven surfaces.
  • Post surgical balance and proprioceptive training that involves single limb standing may begin with adequate knee control is achieved on the operated limb, which typically occurs around 8 weeks post-TKA.
  • Individualised rehabilitation programmes that include strengthening and intensive functional exercises, given through land-based or aquatic programmes, may be progressed as clinical and strength milestones are met.
    Owing to the highly individualised characteristics of these exercises, supervision by a trained physiotherapist is beneficial.

Question 14

Phase 4: 8-12 weeks, up to 1 year post-surgery

Answer 14

• Aim for independent exercise in the community setting
  
  • Continue regular exercise involving strengthening, balance and proprioception training
    Incorporate strategies for behaviour change to increase overall physical activity

Answer 15

• A unicondylar knee replacement (or patellofemoral replacement) may also be performed depending on the extent of disease.
  
  • Several options of anaesthesia are available, and include regional anaesthesia in combination with local infiltration anaesthesia, or general anaesthesia in combination with local infiltration anaesthesia, with the possible addition of peripheral nerve blocks to either option. A torniquet may sometimes be used during surgery.
  • Computer-assisted navigation systems (CAS) or robotic surgery have been introduced in TKA surgery to facilitate surgeon hand motions in limited operating spaces (prospective studies on long term functional outcomes are needed). It allows doctors to perform many types of complex procedures with more precision, flexibility, and control than is possible with conventional techniques.
    CAS are usually associated with minimally invasive surgery (procedures performed through tiny incisions). It is also sometimes used in certain traditional open surgical procedures.