Total Knee Replacement (TKR)

Total knee replacement  (also called total knee arthroplasty), which was first performed in 1968, is a surgical procedure in which the worn out or damaged surfaces of the knee joint are removed and replaced with artificial parts. Total knee replacements are one of the most successful procedures in all of medicine, as it is a relatively safe and effective procedure to relieve pain, correct leg deformity, and help you resume normal activities.

Anatomy

The knee is the largest joint in the body, and is made up of the lower end of the femur (thigh bone), the tibia (upper end of the shin bone), and patella (kneecap). The ends of these three bones where they touch are covered with articular (hyaline) cartilage, a smooth substance that protects the bones and enables them to move easily. The menisci are located between the femur and tibia, and are the soft C-shaped wedges that act as a cushion and helps absorb shock during motion.  Large ligaments hold the femur and tibia together and provide stability, while the long thigh muscles give the knee strength and drive the movements.

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Normal knee anatomy. In a healthy knee, these structures work together to ensure smooth, natural function and movement. 

Indications for Total Knee Replacement

Total knee replacement surgery is commonly indicated for severe osteoarthritis of the knee that has failed to respond to non-surgical treatments. 

Osteoarthritis is the most common form of knee arthritis in which the joint surface cartilage gradually wears away, and it often affects older people.  Over time, the joint cartilage becomes thinner or completely absent exposing bare bone. In addition, the bones become thicker around the edges of the joint and may form bony “spurs”. These factors can cause pain, swelling and restriction in knee movement.

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Total knee replacement may be advised if you have:

• Severe knee pain that limits your routine daily activities (such as walking, getting up from a chair, or climbing stairs).
• Moderate to severe pain that occurs during rest or wakes you from sleep.
• Chronic knee inflammation and swelling that is not relieved with rest, medications, or occasionally injections
• Failure to obtain pain relief from medications, injections, physical therapy, or other non-surgical (conservative) treatments.
• Knee deformity (bow-leg, knock-knee, or other contracture)
• Instability related to the arthritic process.

Recommendations for surgery are based on a patient's pain and disability, and not their age. Most patients who undergo total knee replacement are aged 50 to 80, but each patient must be individually evaluated. Total knee replacements have been performed successfully at all ages, from the young teenager with juvenile chronic arthritis to the elderly patient with degenerative osteoarthritis.

Causes

Any process that can damage the protective smooth layer of joint surface cartilage may lead to osteoarthritis, causing extreme pain and difficulty in performing daily activities. The exact cause of osteoarthritis is not known, but a number of factors are commonly associated with the onset of arthritis, including:

• Injury or trauma to the joint, including knee ligament or meniscal tears
• Fractures at the knee joint, especially those involving the joint surface
• Increased body weight
• Repetitive overuse
• Joint infection (septic arthritis)
• Inflammation of the joint (inflammatory arthritis – the commonest being rheumatoid arthritis)
• Connective tissue disorders (such as systemic lupus erythematosus).

Diagnosis and Orthopaedic Evaluation

The diagnosis and evaluation of knee osteoarthritis, for which knee replacement may be recommended, is based on several components:

• A thorough and detailed medical history – to obtain information about your general health and about the extent of your knee pain and ability to function.  
• A physical examination - This will assess knee range of motion, stability, strength, and overall lower leg alignment.
• X-rays - These images help to determine the extent of damage and deformity in your knee, and typically show narrowing of the joint space.

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(Left) In this x-ray of a normal knee, the space between the bones indicates healthy cartilage (arrows). (Right) This x-ray of a knee that has become bowed from arthritis shows severe loss of joint space (arrows).

• Other tests - Occasionally blood tests, or advanced imaging studies such as a magnetic resonance imaging (MRI) scan, may be needed to determine the condition of the bone and soft tissues of your knee.
• There will be a full discussion about the surgical procedure, including realistic expectations and outcomes, potential risks and complications, as well as any role for non-surgical treatments or prehab (pre-surgery exercise or rehabilitation). You should also provide a full list of medications (prescribed, non-prescription, herbal, and blood thinning) that you take, and timing for stopping any of these will be advised as necessary.

Realistic Expectations for Total Knee Replacement

Over 90% of people who have total knee replacement surgery experience a dramatic reduction of knee pain and a significant improvement in the ability to perform common activities of daily living. In fact, overall satisfaction rates are reported at about 85%, despite the initial painful nature of the procedure. Total knee replacement will not allow you to do more than you could before you developed arthritis, that is, the knee is NOT “bionic”.

With normal use and activity, every knee replacement implant inevitably begins to wear the plastic tibial spacer. Excessive activity or weight may accelerate this normal wear and may cause the knee replacement to loosen, become painful, or to develop swelling. High-impact activities such as running, jogging, jumping, or other high-impact sports should be restricted or avoided for the rest of your life after surgery. Realistic activities following total knee replacement include unlimited walking, swimming, golf, driving, light hiking, biking, ballroom dancing, and other low-impact sports. With appropriate activity modification, knee replacements can last for many years.

Risks and Complications

The complication rate following total knee replacement is low, with significant complications, such as infection, occurring in fewer than 2% of patients. Major medical complications such as heart attack or stroke occur even less frequently. Chronic illnesses may increase the potential for complications. When these complications occur, they can prolong or limit full recovery.

Possible risks and complications associated with total knee replacement surgery include:

• Infection – This may occur in the superficial wound or deep around the prosthesis. It may happen while in the hospital or after you go home, and may even occur years later. Minor infections in the wound area are generally treated with antibiotics. Major or deep infections may require more surgery and including washout or removal of the prosthesis. Any infection in your body can spread to your joint replacement. The incidence of deep infection is reported to occur in 1-1.5% of cases, but this has been reported to be lower in high volume surgeons.
• Blood clots (deep vein thrombosis) - Blood clots in the leg veins are one of the most common complications of knee replacement surgery, and have been reported as high as 25% in some series (A/Prof Woodgate’s current incidence is less than 5%). These clots can be life-threatening if they break free and travel to your lungs (pulmonary embolism). A prevention program, which may include periodic elevation of your legs, lower leg exercises to increase circulation, compression (TED) stockings, calf compressors, early mobilisation, and medication to thin your blood (Clexane injections) is important.  You will also have a Duplex (ultrasound) scan of the lower leg veins 3-5 days post-surgery to look for any signs of DVT formation.
• Knee stiffness - Although an average of 115-120° of motion is generally anticipated after knee replacement surgery, scarring of the knee can occasionally occur, and motion may be more limited, particularly in patients with restricted range of motion before surgery. Ideally you should aim to achieve 90 degrees by day 5-6, but if there is still less than 90 degrees at follow-up after 5-6 weeks, a manipulation under anaesthetic (MUA) is recommended to assist regaining motion.  This will often require 2-3 days in hospital for more intense physiotherapy and analgesia. The incidence of patients requiring MUA is approximately 0.5% (1 in 200).
• Nerve and blood vessel damage – This is rare, though most patients will report a persistent area of numbness to the lateral (outer) side of the surgical wound.
• Ligament injuries – Uncommonly related to pre-surgical damage or excessive releases from soft tissue balancing during the surgery.  If this occurs, a more constrained/stabilising component will be available to compensate.
• Patella (kneecap) dislocation – Whilst the patella may be subluxed or dislocated pre-surgery due to chronic maltracking/malalignmanet, it occasionally is seen post-surgery.
• Plastic liner wear - Although implant designs and materials, as well as surgical techniques, continue to advance, implant surfaces may wear down and the components may loosen or cause secondary changes in the adjacent bone or ligaments.  This can usually be detected on follow-up X-rays, and this is why routine review is scheduled every 1-2 years. There are currently implants available with over 30-year results for longevity, and A/Prof Woodgate will match the appropriate implant to your knee.
• Loosening of the implant – This can occur due to wear of the implant, debonding at the fixation of the cement to bone, or failure of bone ingrowth (if an uncemented implant was used). Deep infection will also need to be excluded.
• Continued pain. A small number of patients continue to have pain after a total knee replacement. This complication is rare and sometimes a clear cause cannot be found. The vast majority of patients experience excellent pain relief following knee replacement.
• Blood transfusion – With modern anaesthetic and surgical techniques, blood transfusion is uncommon in primary (first time) total knee replacement.

Preparing for Knee Replacement Surgery

Medical and Anaesthetic Evaluation

If you are proceeding with knee replacement surgery, you may need review by a physician for a complete medical assessment and to optimize your fitness for the operation. This is likely if you have a significant history of cardiac, respiratory or kidney disease, a strong history of DVT, or are on anticoagulants or other blood thinners. You may also need an early anaesthetic review. Further more complex investigative workup may be then ordered.  This will help ensure that the risks of surgery are minimised.

Preadmission Clinic

You may require a formal preadmission clinic visit a week prior to your scheduled operation. As part of this visit, routine blood tests, urine analysis, ECG and X-rays including a chest X-ray will be performed.  Not all patients need a formal assessment – many of these tests can be arranged in the outpatient setting.

Pre-op and Post-op Guidelines for Knee Surgery

It is important to be fully prepared for your surgical procedure, including having your home made easier to navigate during the recovery phase.  This is outlined in the section “PREOP AND POSTOP GUIDELINES FOR KNEE SURGERY”.

Dental Evaluation

Although the incidence of infection after total knee replacement is very low, an infection can occur if bacteria enter the bloodstream. Any major dental procedures (including tooth extractions and periodontal work) should be completed before undertaking your knee replacement surgery. Further, there should be no active gum or mouth infection present. Following knee replacement surgery, A/Prof Woodgate has an ongoing protocol to cover any dental procedures.  If you plan any dental work, at any time after your knee surgery, please contact A/Prof Woodgate for advice.

Medications

You should previously have informed A/Prof Woodgate of all medications you are currently taking, and he will have informed you of which medications should be ceased and at what time. A/Prof Woodgate will also advise alternatives for the blood thinning medications (should this be necessary). You should bring all your medications with you when you are admitted to hospital.

Urinary Evaluations

Patients with a history of recent or frequent urinary infections should have a urological evaluation before surgery, including a urine analysis. Older men who may have prostate disease should consider completing required treatment before undertaking knee replacement surgery.

Skin and Leg Preparation

There should be no skin infections or irritation on your knee and leg, and ideally no significant lower leg chronic swelling. You will be advised to use a skin antiseptic solution (Chlorhexidine body wash) when showering the night before the operation, and on the day of surgery to clean your leg and sterilize the skin (this decreases the number of bacterial organisms that normally live on the skin and could contribute to potential infection).  Do NOT shave your leg prior to the surgery – this will be done in the operating room if necessary.

Admission to Hospital

The Admissions Office at the Hospital will contact you on the day prior to surgery to notify you of the admission time.  You will also be told when to stop eating and drinking prior to the procedure (this is usually 6 hours for solid foods including milk and juice, and 2 hours for sips of water).

Procedure (Total Knee Replacement)

Before you enter the actual operating room, you will go into an anaesthetic bay, where the anaesthetist will insert a intravenous cannula or “drip” (needle attached to a tube) into the back of your hand. This can be used to administer antibiotics (to help prevent infection), relaxants (to calm you prior to surgery), analgesics (to help prevent you from feeling unnecessary pain) and anaesthetic agents (to make you unconscious during surgery). When it is time for your operation you will be taken around to the operating theatre on a trolley.

The surgery is performed under spinal and/or general anaesthesia.  A tourniquet is positioned on your thigh to prevent blood loss. The operation site will be swabbed with an antiseptic solution and the tourniquet tightened. Sterile drapes (cloths) will be placed so that the only thing showing will be the leg to be operated on.

An incision (approximately 20-30cm) is made through the skin over the affected knee to expose the underlying knee joint. Any soft tissue ligament balancing releases are performed. The damaged menisci and cruciate ligaments are removed to expose the damaged bone surfaces. The tibia is prepared first utilising special guides, followed by preparation of the femur.  Unique spacer blocks allow for confirmation of ligament balance in multiple knee positions To make sure the patella (knee cap) glides smoothly over the new artificial knee, its rear surface is also prepared to receive a plastic component. Using another cutting guide, the undersurface of the patella (knee cap) is sliced off with the bone saw - the front of the patella (with its tendons still attached) is left intact. All these guides remove the damaged portions of the joint and create a smooth surface on which the artificial implants can be attached. Next, the tibial, femoral and patellar components are then secured to the prepared surfaces with bone cement. A plastic piece is inserted on the tibia called an articular surface between the implants to provide a smooth gliding surface for movement. This plastic insert will support the body’s weight and allow the femur to move over the tibia, similar to the original meniscus cartilage. With all the new components in place, the knee joint is tested through its range of motion, as well as to reassess ligament balance. The entire joint is then irrigated and cleaned with a sterile solution. The incision is carefully closed, drains are inserted, a sterile dressing is placed over the incision, and compression dressings are applied. At the end of the surgical procedure, and before the general or sedation anaesthetic is reversed, the anaesthetist will insert a local anaesthetic catheter block (regional block). A catheter is inserted in the femoral nerve sheath in the groin and connected to a Painbuster device to continuously deliver local anaesthetic over 48 hours.  The anaesthetic is then reversed and you will be transferred to the recovery unit. Total knee replacement typically takes 90-120 minutes of surgical time.

For TKR, the implant currently used is the RBK Rotating Bearing High Flexion Knee components.

The Recovery Room

Unlike normal sleep, you will have no sense of the passage of time during the anaesthetic and operation. As soon as you're asleep, you'll feel like you're being woken up and told that operation went very well. As you're waking up you may feel very tired, disoriented, anxious or nauseous. The important thing to realise is that these feelings can be a normal reaction to surgery. Try to relax and take your time in coming back to full consciousness. You may be instructed in some deep breathing and coughing exercises. These are designed to help reduce the risk of contracting pneumonia by clearing any secretions that may have settled in your lungs during the operation.

The nursing staff will closely monitor your stay in the recovery ward until you have fully regained consciousness, which may take a few hours. Then you will be taken back on the trolley to the orthopaedic ward.

Your Hospital Stay

You will most likely stay in the hospital for 5-6 days for a first-time operation (“primary”), and longer for a “revision” operation. After surgery, you will feel some pain, but medication will be given to you to make you feel as comfortable as possible, and will include regular Paracetamol, non-steroidal anti-inflammatory drugs (NSAIDs), and opioids often initially delivered via an intravenous route (PCA or Patient Controlled Analgesia – this allows you to control when the pain-reliving medication is provided). Regular ice with packs should be applied to the knee for 20 minutes every 2 hours. Your leg will have bulky compression bandages applied from the toes to the upper thigh, which will be taken down on day 2.  There will be a drain seen coming through the dressing, which will remove excess blood from within the knee joint – this is removed on either the first or second post-operative day, depending on the losses.  A Painbuster device and catheter will deliver local anaesthetic to the femoral nerve (this will have been inserted by the anaesthetist and is usually removed on the second post-operative day).

As soon as your anaesthetic has worn off, foot and ankle movements are encouraged to also increase blood flow in your leg muscles to help prevent leg swelling and blood clots. You will begin a mobilisation programme on day 2 (the first 24 hours are resting in bed to allow the wound to settle). Mobilisation will commence with a frame, and progress to crutches or a stick. To avoid lung congestion and collapse (known as atelectasis) after surgery, you should breathe deeply and cough frequently to clear your lungs. A simple breathing apparatus called a spirometer (or triflow) may be provided to encourage you to take deep breaths. To minimize the risk of clots (DVT) forming, you will be mobilized early on day 2, long TED (antiembolic) compression stockings applied, as well as inflatable calf compressors, and a blood thinning agent such as Clexane injections will be used.

After 48-72 hours, the PCA machine, drip (intravenous cannula), and bladder catheter are removed, and a regular oral pain programme is started.  Many of these painkilling drugs (especially the opioids) are constipating, and you will be need a bowel care programme incorporating regular aperients/ stool softeners to avoid this distressing complication. 

The physiotherapist will assist you with specific exercises to strengthen your leg and restore knee movement (bending exercises commence on the second day after the bulky initial wound dressing is removed) to allow walking and other normal daily activities soon after your surgery particularly concentrating on getting the knee fully straight and flat by quadriceps contraction. Bending is encouraged but not forced, and always comes once the swelling goes down, though the first goal should be to achieve 90 degrees of knee bend by day 5-6 post surgery (at the time of discharge).

On day 5 (planned discharge day), you will have a Doppler ultrasound scan of the operated leg performed, looking for clots (DVT). The wound dressing will be changed and any advice for planned suture removal will be discussed. You will usually progress onto crutches fully weight bearing for discharge, though walking aids (crutches or a cane) are often needed for at least 6 weeks. 

If you are to be transferred to an inpatient rehabilitation facility, clear instructions will be given by A/Prof Woodgate with regard to wound care, use of stockings, duration of the Clexane (blood thinning) injections, use of ice, suitability and timing of hydrotherapy, importance of your own self-directed exercise programme when not attending formal physiotherapy, and a pain management programme. Many patients fall into the error of trying to stop painkillers before the knee has settled and range of motion has returned, so it is important to gradually wean the strong medication only once significant progress has been made.

Your Recovery at Home

The success of your knee replacement surgery will depend largely on how well you follow A/Prof Woodgate’s instructions once at rehab or after going home during the first few weeks after surgery.

Wound Care

You will have a dissolving suture running beneath your skin on the front of your knee, which may be reinforced with some interrupted nylon skin sutures. The interrupted nylon stitches will be removed several weeks after surgery. The suture beneath your skin will not require removal.  A waterproof dressing will cover the wound for the first 2 weeks, and after this the wound may be left uncovered if it is healing well, but MUST be recovered with a new waterproof dressing when undertaking hydrotherapy. Avoid soaking the wound in water until it has thoroughly sealed and dried, which may take 4-6 weeks.

Diet

Some loss of appetite is common for several weeks after surgery, and a balanced diet is important to help your wound heal and to restore muscle strength.

Activity

Exercise is a critical component of the ongoing home care recovery phase, particularly during the first few weeks after surgery. You should be able to resume most normal activities of daily living within 3 to 6 weeks following surgery. Some pain with activity and at night is common for several weeks after surgery. Your activity program should include:

• A graduated walking program to slowly increase your mobility, initially in your home and later outside when you feel safe.
• Resuming other normal household activities, such as sitting, standing, and climbing stairs (climbing and descending stairs will initially be done one step at a time, gradually returning to a more normal foot-over-foot technique.  It often takes many months for this to occur as the body adapts to the knee artificial knee implants.
• Specific exercises several times a day to restore movement and strengthen your knee, which you may be able to perform without help, but you may have a physiotherapist visiting you at home or at a therapy centre can provide assistance, encouragement and guidance during the first few weeks after surgery.

You will most likely be able to resume driving when your knee bends enough that you can enter and sit comfortably in your car, when your muscle control provides adequate reaction time for braking and acceleration, and as the opioid (narcotic) analgesics are being weaned. Most people resume driving after 6 weeks after surgery, mainly due to the Road Transit Authority Guideline for safe return to driving being set at 6 weeks.

Avoiding Problems After Surgery

Blood Clot Prevention

Follow A/Prof Woodgate’s instructions carefully to reduce the potential for blood clots developing during the first several weeks of your recovery. The routine duration for Clexane (blood thinning) injections that you started in the hospital is for approximately 4 weeks total, though this may be modified if there is a past history of DVT or other clot history, or if you have been using alternative blood thinning agents prior to surgery.

A/Prof Woodgate MUST be notified immediately if you develop any of the following warning signs:

• Warning signs of possible blood clots in your leg include:
  • Increasing pain in your calf
  • Tenderness or redness above or below your knee
  • New or increasing swelling in your calf, ankle, and foot
• Warning signs of pulmonary embolism (a blood clot has travelled to your lung) include:
  • Sudden shortness of breath
  • Sudden onset of chest pain
  • Localized chest pain with coughing
  • Coughing up blood.

Preventing Infection

A common cause of infection following total knee replacement surgery is from bacteria that enter the bloodstream during dental procedures, urinary tract infections, or skin infections. These bacteria can lodge around your artificial knee replacement and cause an infection.

After knee replacement, you should take antibiotics prior to dental work, including dental cleanings, or before any surgical procedure that could allow bacteria to enter the bloodstream.

Warning signs of possible knee replacement infection include:

• Persistent fever (higher than 38 degrees orally)
• Shaking chills
• Increasing redness, tenderness, or swelling of the knee wound
• Drainage or discharge from the knee wound
• Increasing knee pain with both activity and rest.

Notify A/Prof Woodgate immediately if you develop any of these signs of a possible knee replacement infection.

Avoiding Falls

A fall during the first few weeks after surgery can damage the new knee and may result in the need for further surgery. Stairs can be a particular hazard until your knee is strong and mobile. You should use a cane, crutches, a walker, handrails, or have someone to help you until you have improved your balance, flexibility, and strength. You will be advised which assistive aides will be required following surgery and when those aids can safely be discontinued.

Outcomes of Total Knee Replacement

How Your New Knee Is Different

Improvement of knee motion is one of the goals of total knee replacement, but restoration of full motion is uncommon. The motion of your knee replacement after surgery can be predicted by the pre-operative range of motion you have in your knee. Most patients can expect to be able to almost fully straighten the replaced knee and to bend the knee sufficiently to climb stairs and get in and out of a car, as well as being able to sit comfortably – most patients achieve up to 120 degrees range or more. Kneeling is no recommended due to the potential for shearing forces across the plastic tibial tray insert which may lead to earlier failure. Almost all patients feel some numbness in the skin around your incision, especially on the lateral (outer) side of the wound. You also may feel some stiffness, particularly with excessive bending activities or after prolonged sitting. Some clicking of the metal and plastic with knee bending or walking is often reported and is to be expected.

These differences often diminish with time and most patients find them to be tolerable when compared with the pain and limited function they experienced prior to the surgery.

Artificial knee replacements may activate metal detectors required for security in airports and some buildings – you should inform the security agent about your knee replacement if the alarm is activated.

Protecting Your Knee Replacement

After surgery, make sure you also do the following:

• Participate in regular light exercise programs to maintain proper strength and mobility of your new knee.
• Take special precautions to avoid falls and injuries. If you break a bone in your leg, further surgery may be required.
• Make sure your dentist knows that you have a knee replacement. A/Prof Woodgate will advise about a prophylactic antibiotic protocol to decrease the potential for seeding infection to your new knee.
• Routine periodic follow-up examination and x-rays are important to monitor the ongoing good function of the new knee, usually every second year once through the initial 12-month healing period.

If you have any concerns whatsoever about your operation and progress, It is important that you contact A/Prof Woodgate’s office directly after discharge.  We will always be available to answer any queries.