Knee Replacement

Surgical replacement of the knee joint

Many patients over the age of 65 have some form of arthritis in the knees. This is usually due to osteoarthritis, although it can be due to other forms of arthritis such as rheumatoid arthritis. In arthritis the cartilage lining of the joint wears away. In severe cases this results in bone grinding against bone. In many cases the symptoms can be controlled with non operative treatment. However in many cases a knee replacement may be recommended.

REASONS FOR TOTAL KNEE REPLACEMENT

Your General Practitioner and Orthopaedic Surgeon may recommend knee replacement surgery for the following reasons:

• Severe pain that restricts work, recreation and activities of daily living
• Pain that disturbs sleep at night
• Pain that occurs even at rest
• Pain that is not relieved by analgesics, anti inflammatories, physiotherapy or the use of a stick.

Normally severe arthritis would be confirmed by X-rays taken with the patient standing.

BEFORE SURGERY

Admission papers will include a consent form and questionnaire. These will need to be completed and sent to the hospital where you are having your surgery. You should inform your surgeon or Anaesthetist of any medical conditions or past treatments that may affect your anaesthetic, operation or after care. This should include any allergies, prolonged or excessive bleeding after injury or surgery, previous problems with blood clots in the legs or the lungs, gout, diabetes or any wound healing problems. Normally pre operative investigations would be organised and include blood tests, an electrocardiogram (ECG) and a mid stream urine specimen. A blood sample will also be taken to send to the Blood Bank in case you require blood transfusion after surgery.

Non steroidal anti inflammatory medications and Aspirin cause thinning of the blood and therefore contribute to excessive bleeding. These should be stopped a week before surgery. Stronger blood thinners, such as Warfarin will also need to be stopped prior to surgery. Normally your surgeon will liaise with the physician who has placed you on the medication, to come up with a safe plan for this.

You will normally be admitted to the hospital on the morning of surgery. The staff of the hospital will have contacted you to let you know what time to come in. It is important to bring all your relevant X-rays and investigation results with you. You should also bring all your current medications.

You must contact your surgeon’s office if you have any infection, pimples, broken skin or ulcers anywhere on the limb that is having surgery.

THE SURGICAL PROCEDURE

Knee arthroplasty is normally performed under spinal or general anaesthetic. Your Anaesthetist will discuss the relative benefits of each of these with you, prior to surgery. During the procedure an incision is made through the front of your knee. The knee cap (patella) and associated tendon are carefully moved aside. Special cutting guides and surgical tools are used to remove the worn out surfaces of the femur, tibia and patella. The surfaces are carefully prepared to accommodate the size of the implants. A metal prosthesis, similar in shape and size to the end of the femur, is cemented to the bone. A metal plate is attached to the top of the tibia, again with bone cement. A plastic component is then inserted to act as a cushion between the two metal surfaces. The patella is resurfaced with moulded plastic cemented into place. The ligaments around the knee are carefully preserved as they are necessary for normal joint function and stability. Occasionally some of the ligaments are tight because of the arthritis and these are carefully released during the procedure if necessary. Once the prostheses are inserted the surgeon carefully checks that the knee has a full range of motion and the ligaments are well balanced. The knee is then stitched closed over a drain. The procedure normally takes approximately 1½ hours for one side, and 3 hours if both sides are being done.

RECOVERY AFTER KNEE REPLACEMENT SURGERY

Immediately after surgery you are transferred to a Recovery Room. You will have a dressing on the knee with a drainage tube to reduce swelling. You will also wake up with a urinary catheter in place. You will be wearing elastic stockings to reduce the chance of blood clots. Intensive pain relief will be provided immediately post operatively and for the period following surgery. This normally controls the pain well but you can expect some pain and discomfort. It is a good idea to discuss your pain relief with your Anaesthetist before surgery.

Normally patients spend 5-7 days in hospital after surgery. The surgical drain is removed the day after surgery and the patient sits up in a chair and commences standing and walking. Blood is taken to check the blood count and kidney function on the day after surgery. The urinary catheter is normally removed the second day after surgery and the bandage is reduced. Rehabilitation commences the day after surgery and this involves exercises to improve the strength and range of motion of the knee and to help the patient walk. On the first day after surgery a Physiotherapist will assist the patient in getting out of bed and walking a short distance. An ice pack and pain relief is used to help with discomfort and swelling, and to allow the patient to undertake rehabilitation. If these do not adequately control the pain then the nursing staff or your surgeon should be notified. The hospital will organise outpatient physiotherapy to continue after discharge. This is important in the first 6 weeks following surgery as it will help regain the strength and range of motion in the knee.

If at any stage after discharge there is redness, discharge or inflammation of the wound then the GP should be notified, or your surgeons rooms. Dr Limbers will see you with repeat X-ray at 6 weeks following surgery.

Much of the recovery from a total knee replacement will be obtained in the first 2-3 months. However full recovery is a year or more and some patients continue improving for 2 years. You can expect to be able to drive a car at 6 weeks after a total knee replacement. If you had a left total knee replacement then you could drive an automatic car after 2 weeks. There will be swelling in the knee for at least 3-6 months following surgery. This is normal and will gradually resolve. It is generally possible to travel from 6 weeks following surgery.

RESULTS OF KNEE REPLACEMENT SURGERY

The vast majority of patients are very happy with the long term results of knee replacement surgery. Most patients report little or no pain. Approximately 90% of total knee replacements are still functioning after 10 years and approximately 80% are functioning after 20 years.

LOOKING AFTER YOUR TOTAL KNEE REPLACEMENT

It is important to look after your total knee replacement as your prosthesis is designed for activities of daily living and for leisure activities. It is not designed for intense or contact sports. Repetitive jarring of the joint caused by regular running or jumping can result in loosening of the prosthesis. Returning to recreational activities such as gardening, golf, bowls, doubles tennis or sailing can generally be managed after 2-3 months, provided an appropriate rehabilitation program has been undertaken.

Patients are generally unable to kneel after a knee replacement. This is due to the scar being painful with the direct pressure of kneeling. In addition, because full range of motion is often not obtained after knee replacement patients will often find it difficult to get up from a kneeling position. The skin on the outer surface of the scar is numb after knee replacement surgery. This means that cuts and abrasions may occur more easily, which in turn could lead to infection. If a patient wishes to kneel after knee replacement it is better to kneel on a clean, soft surface.

POSSIBLE COMPLICATIONS AFTER KNEE REPLACEMENT

Complications after knee replacement surgery are rare and occur in less than 5% of patients. However they can be significant and as with any surgery, you should be aware of potential complications but not alarmed. It is a good idea to discuss them with your surgeon.

Possible complications include:

• Infection – this happens in approximately 2% of patients and may occur in the early months after the operation or later in life. To prevent this it is a good idea to take antibiotics before and after other surgery or dental work. Surgery is carried out under strict sterile conditions in the operating theatre, under antibiotic cover. Nonetheless infections may still occur. Most infections are superficial and can be treated with antibiotics. However sometimes there may be more serious, deep infections and require further surgery. This may include removal of the prosthesis followed by further revision surgery plus prolonged antibiotics.
• Blood clots – these can form in the deep veins of the leg and on occasion may break off and travel to the lung. You will be given small doses of anti coagulants in the weeks following surgery to reduce the chance of this occurring. Significant clots can be life threatening and require immediate treatment with blood thinning medications. This is usually Warfarin.
• Stiffness – a knee replacement is normally stiff for up to three months and early physiotherapy helps to overcome this. The average knee replacement can be expected to bend to approximately 120°. Occasionally the range of motion of a knee replacement is significantly less than this. This is more likely if the knee was very stiff prior to surgery. Occasionally a manipulation under general anaesthetic is required 1-2 months following surgery to help overcome the stiffness.
• Nerve Damage – it is normal for the skin on the outer surface of the incision to be numb following knee replacement. However in a very small proportion of cases there is significant damage to the nerves leading to weakness and numbness in the foot. This is very rare and usually recovers spontaneously.
• Excessive Bleeding – this can result in a haematoma. It occurs in less than 1% of all cases. Occasionally this results in wound breakdown with the necessity for further surgery to re-suture the wound.
• Re-operation for a loose prosthesis – this is rare. The prosthesis may come loose, causing pain and requiring further revision surgery. This may happen due to trauma or infection but in many cases there is no known cause.

You should contact your local doctor or surgeon if you have temperatures higher than 38.5°, severe pain, heavy bleeding, redness around the incision, worsening flexibility or inability to bend the knee.