A total knee replacement (TKR) or total knee arthroplasty is a surgery that replaces an arthritic knee joint with an 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 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 co-operative 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 chair, gardening, etc
- Pain waking you at night
- Deformity- either bowleg or knock knee
Prior to surgery you will usually have tried some simple treatments such as simple analgesics, weight loss, anti-inflammatory medications, modification of your activities, walking sticks, physiotherapy.
Once these have failed it is time to consider surgery. Most patients who have TKR are between 60 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.
- Your surgeon will send you for routine blood tests and any other investigations required prior to your surgery
- You will 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 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
- You will be admitted to 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 mins prior to surgery, you will be transferred to the operating theatre
Each knee is individual and knee replacements take this into account by having different sizes for you 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 theatre under spinal or general anaesthesia. You will be on you back and a tourniquet applied to your upper thigh to reduce blood loss. Surgery takes about two hours .
The surgeon cuts down to the bone to expose the bones of the knee joint.
The damaged portions of the femur and tibia are then cut at the appropriate angles using specialized jigs. 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) may be replaced depending on a number of factors depending on surgeon’s choice.
The real components are then inserted with or without cement and the knee is again checked to make sure things are working properly. The knee is then carefully closed and drains usually inserted, and the knee dressed and bandaged.
When you wake up, you will be in the recovery room with intravenous drips in your arm, a tube (catheter) in you bladder and a number of other monitors to check your vital observations. You will usually have a button to press for pain called Patient Controlled Analgesia (PCA).
Once stable, you will be taken to the ward. The post-op protocol is surgeon dependant, but in general your drain will come out at 24 hours and you will sit out of bed and start moving you knee and walking on it within a day or two of surgery. The dressing will be reduced usually on the 2nd post of day to make movement easier. Your rehabilitation and mobilization will be supervised by a physiotherapist.
To avoid lung congestion, it is important to breathe deeply and cough up any phlegm you may have.
Your orthopaedic surgeon will use one or more measures to minimize blood clots in your legs, such as inflatable leg coverings, stockings and injections into your abdomen to thin the blood clots or DVT’s, which will be discussed in detail in the complications section.
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 be in hospital for 5-7 days and then either go home or to a rehabilitation facility depending on your needs. You will need physiotherapy on your knee following surgery.
You will be discharged on a walking aid either on frame or crutches and usually progress to a walking stick at six weeks.
Your sutures are sometimes dissolvable but if not are removed at approx 10 days.
Bending you knee is variable, but by 6 weeks should be to 90 degrees. The aim is to get 110-115 degrees of movement.
Once the wound is healed, you can take a 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 be able 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 usually have a 6 weeks check up with your surgeon who will assess your progress. You should continue to see your surgeon 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 recognized 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.
If you ever have any unexplained pain, swelling, redness or if you feel unwell you should see your doctor as soon as possible.
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 ongoing health concerns, prolonged hospitalization 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 theatre and under anaesthetic the knee is bent for you.
The plastic liner eventually wears out over time, usually 10 to 15 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 which may require antibiotics or rarely further surgery.
- Cosmetic Appearance
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 loose contact with each other or the plastic insert can lose contact with the tibia (shinbone) or the femur (thigh bone).
- Patella problems
Patella (knee cap) can dislocate that is, it moves out of place and it can break or loosen.
- Ligament injuries
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 fix these, you may require surgery.
Discuss your concerns thoroughly with your orthopaedic surgeon prior to 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 peoples quality of life, taking away pain and improving function. In general 90-95% of knees survive 15 years depending of 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 there prior to making a decision. If you are undecided, it is best to wait until you are sure this is the procedure for you.