A Total Knee Replacement (TKR) or Total Knee Arthroplasty is a surgery that replaces an arthritic knee joint with artificial metal or plastic replacement parts called the ‘prostheses’.
The procedure is usually recommended for older patients who suffer from pain and loss of function from arthritis and have failed results from other conservative methods of therapy.
The typical knee replacement replaces the ends of the femur (thigh bone) and tibia (shin bone) with plastic inserted between them and usually the patella (knee cap).
Other causes include
- Trauma (fracture)
- Increased stress e.g., overuse, overweight, etc.
- Connective tissue disorders
- Inactive lifestyle e.g., Obesity, as additional weight puts extra force through your joints which can lead to arthritis over a period of time
- Inflammation e.g., Rheumatoid arthritis
In an Arthritic Knee
- The cartilage lining is thinner than normal or completely absent. The degree of cartilage damage and inflammation varies with the type and stage of arthritis.
- The capsule of the arthritic knee is swollen
- The joint space is narrowed and irregular in outline; this can be seen in an X-ray image.
- Bone spurs or excessive bone can also build up around the edges of the joint
The combinations of these factors make the arthritic knee stiff and limit activities due to pain or fatigue.
The diagnosis of osteoarthritis is made on history, physical examination & X-rays.
There is no blood test to diagnose Osteoarthritis (wear & tear arthritis).
The decision to proceed with TKR surgery is a cooperative one between you, your surgeon, family and your local doctor.
The benefits following surgery are relief of symptoms of arthritis. These include
- Severe pain that limits your everyday activities including walking, shopping, visiting friends, getting in and out of a chair, gardening, etc.
- Pain waking you at night
- Deformity- either bowleg or knock knees
Prior to surgery you will usually have tried some conservative treatments such as simple analgesics, weight loss, anti-inflammatory medications, modification of your activities, canes, or physical therapy.
Once these have failed it is time to consider surgery. Most patients who have TKR are between 50 to 80 years, but each patient is assessed individually and patients as young as 20 or old as 90 are occasionally operated on with good results.
Patient specific instruments (PSI)
My preference is to use patient specific instruments (PSI) for all elective total knee replacements. Patient-specific guides involve acquiring imaging data several weeks prior to the surgery, and then building a model of the knee within a computer. This information is acquired using an MRI scan, and a long-leg standing x-ray. The surgeon then uses this anatomical model of the actual patient to plan the position of the implants prior to surgery. This allows assessment of sizing, precise positioning of the implants, and also gives indication of some of the specific problems that the surgeon may face. This might include how to deal with severe deformity, sizing of smaller or larger patients, and alignment issues.
Once the surgeon has finalised the plan for surgery, patient specific cutting guides are 3D printed. The guides are then sterilised, and shipped in time for the operation. The guides are made to fit only that specific knee. These are designed to be fitted to the knee during surgery and pinned in place. These guides then have pre-made slots for saw cuts or for guide pins, which the surgeon uses to perform the knee replacement. During the surgery the surgeon verifies the cutting positions of the guide with landmarks within the knee, to ensure that correct cuts are made. This is a critical step in insuring precise surgery.
The process from imaging to surgery takes around 5-6 weeks.
- Your surgeon will send you for routine blood tests and any other investigations required prior to your surgery
- You may be asked to undertake a general medical check-up with a physician
- You should have any other medical, surgical or dental problems attended to prior to your surgery
- Make arrangements for help around the house prior to surgery
- Cease aspirin or anti-inflammatory medications 10 days prior to surgery as they can cause bleeding
- Cease any naturopathic or herbal medications 10 days before surgery
- Stop smoking as long as possible prior to surgery
Day of your surgery
- You will be admitted to the hospital, usually on the day of your surgery
- Further tests may be required on admission
- You will meet the nurses and answer some questions for the hospital records
- You will meet your Anaesthetist, who will ask you a few questions
- You will be given hospital clothes to change into and have a shower prior to surgery
- The operation site will be shaved and cleaned
- Approximately 30 minutes prior to surgery you will be transferred to the operating room
Precise surgical planning is performed prior to surgery with the aid of computer assisted templating. Each knee is individual and knee replacements take this into account by having different sizes for your knee. If there is more than the usual amount of bone loss, sometimes extra pieces of metal or bone are added.
Surgery is performed under sterile conditions in the operating room under spinal and/or general anaesthesia. You will be on your back and a tourniquet applied to your upper thigh to reduce blood loss. This is only inflated during implantation of the knee components which is typically for only 7-8 minutes. Surgery takes approximately two hours.
A midline incision is performed and the bones of the knee joint are exposed.
The damaged portions of the femur and tibia are then cut at the appropriate angles using 3D printed patient specific cutting guides. Trial components are then inserted to check the accuracy of these cuts and determine the thickness of plastic required to place in between these two components. The patella (knee cap) is also resurfaced during the procedure.
The real components are then inserted with bone cement and the knee is again checked to make sure things are working properly. The knee is then carefully closed with a dissolvable skin suture, dressed and bandaged.
When you wake, you will be in the recovery room with intravenous drips in your arm, a tube (catheter) in your bladder and a number of other monitors to check your vital observations. You will have an adductor canal catheter inserted into the thigh. This is a special pain catheter that consists of a continuous infusion of local anaesthetic that is connected to a reservoir and has a button attached to allow for patient controlled analgesia. The catheter provides excellent pain relief for 2-3 days post surgery targeting the precise area of trauma. This avoids the typical side effects such as nausea, vomiting and drowsiness associated with standard pain relief medication. The nerve block only targets the sensory supply and avoids any muscles surrounding the knee allowing relatively pain free and early mobilisation.
Once stable, you will be taken to the ward. Your urinary catheter and intravenous drip will be removed day 1 post surgery. The dressing will also be reduced and changed to a thigh high TED stocking to make movement easier. Your rehabilitation and mobilisation will be supervised by a physiotherapist.
To avoid lung congestion, it is important to breathe deeply and cough up any phlegm you may have.
A lot of the long term results of knee replacements depend on how much work you put into it following your operation.
Usually, you will remain in the hospital for 2-3 days. Then, depending on your needs, either return home or proceed to a rehabilitation facility. You will need physical therapy on your knee following surgery.
You will be discharged on a walker or crutches and usually progress to a cane at 4-6 weeks.
I typically review all wounds 10-14 days post surgery.
Bending your knee is variable, but by 6 weeks should bend to at least 100 degrees. The goal is to obtain 135 degrees of movement.
Once the wound is healed, you may shower. You can drive at about 6 weeks, once you have regained control of your leg. You should be walking reasonably comfortably by 6 weeks.
More physical activities, such as sports previously discussed, may take 3 months to do comfortably.
When you go home you need to take special precautions around the house to make sure it is safe. You may need rails in your bathroom or to modify your sleeping arrangements, especially if they are up a lot of stairs.
You will be reviewed again 6 weeks post surgery with progress x-rays. I will continue to see you for the rest of your life to check your knee and take X-rays. This is important as sometimes your knee can feel excellent but there can be a problem only recognised on X-ray.
You are always at risk of infections especially with any dental work or other surgical procedures where germs (Bacteria) can get into the blood stream and find their way to your knee. Prior to any invasive dental work, you will need to take oral antibiotics the day before, day of and day after the dental work.
If you ever have any unexplained pain, swelling or redness or if you feel generally poor, you should see your doctor as soon as possible.
Risks and Complications
- As with any major surgery, there are potential risks involved. The decision to proceed with the surgery is made because the advantages of surgery outweigh the potential disadvantages
- It is important that you are informed of these risks before the surgery takes place
Complications can be medical (general) or local complications specific to the Knee
Medical complications include those of the anaesthetic and your general well being. Almost any medical condition can occur so this list is not complete. Complications include:
- Allergic reactions to medications
- Blood loss requiring transfusion with its low risk of disease transmission
- Heart attacks, strokes, kidney failure, pneumonia, bladder infections Complications from nerve blocks such as infection or nerve damage Serious medical problems can lead to on-going health concerns, prolonged hospitalisation or rarely death
Infection can occur with any operation. In the knee this can be superficial or deep. Infection rates vary. If it occurs, it can be treated with antibiotics but may require further surgery. Very rarely your new knee may need to be removed to eradicate infection.
Blood Clots (Deep Venous Thrombosis)
These can form in the calf muscles and can travel to the lung (Pulmonary embolism). These can occasionally be serious and even life threatening. If you get calf pain or shortness of breath at any stage, you should notify your doctor.
Stiffness in the Knee
Ideally your knee should bend beyond 100 degrees but on occasion, the knee may not bend as well as expected. Sometimes manipulations are required; This means going to the operating room where the knee is bent for you and under anaesthetics.
The plastic liner eventually wears out over time, usually 15 to 20 years and may need to be changed.
Wound Irritation or Breakdown
The operation will always cut some skin nerves, so you will inevitably have some numbness around the wound. This does not affect the function of your joint. You can also get some aching around the scar. Vitamin E cream and massaging can help reduce this.
Occasionally, you can get reactions to the sutures or a wound breakdown that may require antibiotics or rarely, further surgery.
The knee may look different than it was because it is put into the correct alignment to allow proper function.
Leg length inequality
This is also due to the fact that a corrected knee is more straight and is unavoidable.
An extremely rare condition where the ends of the knee joint lose contact with each other or the plastic insert can lose contact with the tibia (shinbone) or the femur (thigh bone).
Patella (knee cap) can dislocate. This means it moves out of place and it can break or loosen.
There are a number of ligaments surrounding the knee. These ligaments can be torn during surgery or break or stretch out any time afterwards. Surgery may be required to correct this problem.
Damage to Nerves and Blood Vessels
Rarely these can be damaged at the time of surgery. If recognized they are repaired, but a second operation may be required. Nerve damage can cause a loss of feeling or movement below the knee and can be permanent.
Fractures or breaks in the bone can occur during surgery or afterwards if you fall. To repair these, you may require surgery.
Surgery is not a pleasant prospect for anyone, but for some people with arthritis, it could mean the difference between leading a normal life or putting up with a debilitating condition. Surgery can be regarded as part of your treatment plan—it may help to restore function to your damaged joints as well as relieve pain.
TKR is one of the most successful operations available today. It is an excellent procedure to improve the quality of life, take away pain and improve function. In general 90-95% of knee replacements survive 15 – 20 years, depending on age and activity level.
Surgery is only offered once non-operative treatment has failed. It is an important decision to make and ultimately it is an informed decision between you, your surgeon, family and medical practitioner.
Although most people are extremely happy with their new knee, complications can occur and you must be aware of these prior to making a decision. If you are undecided, it is best to wait until you are sure this is the procedure for you.