Total (Unicompartmental) Knee Replacement

About Total Knee Replacement

Arthritis leads to the weight-bearing surfaces of the knee joint to become worn away. The cartilage layer is damaged and lost and is no longer smooth, this leads to stiffness and pain in the joint. Eventually the joint wears out to such an extent that the bone of the femur grinds on the bone of the tibia as most of the cartilage is lost.

The two common types of arthritis are osteoarthritis (generalised wear and tear of the joint which often is age-related or post-traumatic) and rheumatoid arthritis (inflammatory arthritis). The main indication for a knee replacement is worsening pain that has not resolved with non-operative measures (pain relief medications, weight loss, physiotherapy, etc.) and is markedly affecting your quality of life.

Osteoarthritis either develops in just one compartment of the knee, inner (medial) compartment, outer (lateral) compartment or under the knee cap (Patello-femoral compartment), but can involve 2 or all 3 compartments of the knee as well. When only one compartment is involved, a uni-compartmental knee replacement (UKR) is the operation of choice and is designed to replace the worn joint surfaces on one side of the joint, thereby relieving pain and improving function. The operation can be performed through a smaller incision (around 12cm – 15cm) which allows quicker healing and recovery.

If the arthritis involves more of the knee then a total knee replacement (TKR) may be recommended. This decision may sometimes be made at the time of surgery when the surgeon can directly inspect the joint surfaces. A TKR replaces the surfaces of the knee with metal and plastic in between. Sometimes a single fully plastic tibial component is used. Rarely the patellar surface (under the knee cap) is replaced with a plastic button, which glides over the metal surface of the femoral replacement, however, when the patella is satisfactory, it may not require surgery. To be able to replace the surface of the knee joint a 20cm incision is made down the front of the knee and the joint opened. The arthritic joint surfaces are removed and the bone is shaped so that the joint replacement components can sit firmly on the bone. The replacement parts are positioned and held in place with bone cement.

Benefits of a Total / Uni-compartmental Knee replacement

The main benefit of this type of surgery is relief of pain. Patients may also notice an improvement of function, allowing them to walk easier and further. Daily activities should become more comfortable and quality of life improved. Some patients may find an improved range of movement after the surgery, although this cannot be guaranteed. The main predictor for range of motion after the operation is range of motion in the knee before the operation.

Before Surgery

Exercises to do

Being active while you wait for surgery is important. People with a painful knee joint are often afraid to be physically active because they worry they may be doing more harm than good. This is not the case. In fact, research has shown that exercise can help decrease pain, improve leg strength and help keep your heart in good condition before surgery. If you have not been regularly active, remember to speak to your GP before starting to exercise.

Endurance activities are good for your heart, lungs, circulation and muscles. Some suggestions for endurance exercises include walking, swimming or use of a stationary bike. If you have not been involved in any regular exercise, it is important to start slowly. Your goal is to be physically active every day. Begin with a few minutes and gradually progress until you can exercise at least 3 times per week for 20 to 30 minutes at a time. No matter which activity you choose to perform, you should be able to carry on a conversation or talk comfortably while exercising without an increased shortness of breath.

Being involved in an exercise program before your surgery will help in your recovery after surgery. After your surgery a team of physiotherapists, occupational therapists and nurses will help you regain your strength, endurance and improve your overall function.

Walking and leg strengthening exercises are an important part of your rehabilitation after your joint replacement surgery

Potential Complications And How To Reduce Them

Despite the success of total joint replacement, there is a small risk of developing complications. These complications can develop because of health problems, the anaesthesia or the surgical procedure itself.

Possible local complications include: surgical site infection, damage to blood vessels and nerves, blood loss possibly requiring blood transfusion, bone or implant fracture, increased bone formation around the joint, dislocation of the joint, altered limb length, early wear of the prosthesis, and persistent or worsened pain and stiffness in the joint that was replaced. These complications may require additional surgery to improve your function.

Other medical complications include the risk of developing a deep venous thrombosis, pulmonary embolism, heart attack, stroke and even death. Although the likelihood of such complications occurring is low, your surgical team will make every effort to minimize the risk as much as possible. Your surgeon, anaesthetist and medical team will discuss these issues with you before surgery. Please make sure all your questions are addressed when you meet with your surgical team.

Infection is a possible complication of any surgery. The risk is reduced through careful surgical technique and the use of antibiotics before your surgery. Bacteria can travel through your bloodstream from infection elsewhere in your body to your new joint, i.e. from your throat, teeth, skin or urine. This is why it is important to have all infections assessed and treated before your surgery, as well as after surgery to protect your new joint. Antibiotics are administered intravenously at the time of your surgery. (Any allergy to any known antibiotics should be brought to the attention of your surgeon or anaesthetist). Despite these measures, there is still a chance of developing an infection but this is less than 2%. Normally these are superficial wound infections that resolve with a course of antibiotics. Occasionally serious infections occur that require further hospitalisation and treatment. Sometimes they necessitate removal of the knee replacement for a period of time; antibiotics are administered via a drip for a few weeks, prior to re-implantation of another knee replacement.

Breathing Problems such as pneumonia can occur after surgery. It is important to do several deep-breathing and coughing exercises every half hour when awake the first few days after surgery. This helps provide oxygen to your lungs and keeps your airways clear. Sitting up, getting out of bed as soon as possible and being active also helps prevent breathing problems.

Cardiovascular Complications (heart problems) can occur due to the stress of surgery. Surgery puts an additional workload on the heart. In patients with known heart disease, this can increase the risk for abnormal heart beats, chest pain or very rarely, heart attack. These complications can also happen in patients with no known heart problems. This is why it is important to have a thorough health assessment before your surgery.

Deep Vein Thrombosis (DVT) are blood clots which can develop in the deep veins of your legs. This is often associated with lack of movement, so getting out of bed and being active as early as possible is encouraged. It is important to move your ankles up and down several times an hour after surgery. This is called “ankle pumping”. You should also tighten and release the muscles in your legs. These exercises promote good circulation. Anticoagulants (blood thinners) will also be used to prevent blood clots. They are given in either a pill or needle form. A combination of immobilisation of the limb, smoking and the oral contraceptive pill or hormonal replacement therapy all multiply to increase the risk of a blood clot. Any past history of blood clots should be brought to the attention of the surgeon prior to your operation. The oral contraceptive pill, hormonal replacement therapy and smoking should cease 6 weeks prior to surgery to minimise the risk.

Pulmonary Embolism can occur when blood clots from the deep veins in the legs or pelvis break off, travel up to the lung and lodge there. If the clot is large enough, blood circulation to the lungs may be cut off. This is a serious complication. Anticoagulants (blood thinners) are given after surgery to prevent clot formation. Ankle pumping and early activity will also help prevent this complication.

Urinary Problems such as difficulty passing urine, can happen following any type of surgery. Sometimes a catheter (soft plastic tube) is placed in the bladder to drain urine. The catheter can be left in place for a few days or removed immediately after the bladder has been emptied. Let your nurse know if you have problems passing urine. Following spinal anaesthesia you may pass some urine without being aware of it. This is normal and can happen during the first few hours until the spinal anaesthesia wears off.

Nausea is common after surgery. Medication may be given to settle your stomach, so let your nurse know if you are experiencing this. In order to minimize nausea, it is important to take your pain pills with food to protect your stomach.

Paralytic Ileus is a distention of the bowel with gas. This can happen when the bowels stop working properly. As a result, gas builds up and causes abdominal discomfort, bloating and vomiting. To prevent this, early activity is important to stimulate your bowels to function normally.

Constipation can occur because pain medication can make your bowels sluggish. Stool softeners are given twice a day to help prevent this. If they are not effective, ask your nurse for a laxative. Make sure your bowels have moved the day before surgery to help prevent problems after surgery. Lots of fluid, a high fibre diet and activity also help.

Allergic reactions can happen after surgery and vary from a mild rash to an intense reaction that can interfere with your breathing. Please let us know if you have any allergies. They will be documented in your medical record. We will also provide you with an allergy alert bracelet to be worn while you are here.

Skin Irritation and bedsores are caused by pressure from lying in bed. It is important to change your position frequently while in bed and to get up as much as possible after surgery. The nurses and therapists will help you.

Confusion and Delirium can sometimes occur in older people after surgery. You may behave differently, and see or hear things that aren’t really there. This usually resolves in a few days, but can last for several weeks. Many things can contribute to this, such as the anaesthetic, pain medication, lack of sleep, and alcohol withdrawal. It is important to let us know if you have experienced this with previous surgeries. Wearing your glasses and hearing aids can help if you experience this. We also recommend that you reduce your alcohol intake several weeks before your surgery. If you have experienced postoperative confusion in the past, it is helpful to have a relative sit with you after surgery.

Stiffness, sometimes the knee becomes stiff after surgery (1%) due to scar tissue forming inside the knee. If this happens the knee may require a manipulation under a second general anaesthetic to help regain movement.

Pain following a TKR/UKR: a small number of people after knee replacement surgery continue to experience some pain. Sometimes no obvious mechanical cause for the pain can be found. Research and studies done have shown that 10 – 15% of patients still have some ongoing pain and are not fully satisfied after their surgery. There isn’t any specific reason to explain why this is the case but the majority of this subgroup of patients still feel that this post-operative pain is still better than their previous arthritic pain and doesn’t impede on their function. An important point to note is that overall recovery and improvement following a Total Knee Replacement can sometimes take up to 2 years.

If you are in this group, you will be investigated further to rule out any significant causes for this pain. Treatment for this involves medical management of the pain, and specialist rehabilitation.

Excessive Bleeding: Inevitably some blood is lost at the time of surgery. Sometimes people lose larger volumes of blood and a transfusion may be required. Bleeding is more likely to occur with patients taking aspirin or other anti-inflammatory drugs. They should be stopped at least one week prior to surgery.

Tendon, nerve or blood vessel damage: Very rarely these structures can be injured during the operation. Normally they recover, but occasionally patients may experience extensive bruising or have difficulty moving their foot up and down. Often after a knee replacement patients have a small patch of numbness to the outside of the scar due to small nerves in the skin being damaged; this normally does not cause problems and often diminishes with time.

Aseptic loosening requiring Revision surgery Over time the components of the knee replacement can wear out or become loose. This normally presents with worsening pain and may require further surgery to put a new knee in. On average, about 85-90% of the TKRs will last 14-15 years and about 85-90% of the UKRs will last 9-10 years.

Dislocation of the bearing (specific to UKR) The UKR has a mobile plastic bearing. Rarely this can dislocate and require further surgery to reposition it (<1%).

Remember…
Getting out of bed and walking as soon as you are able will help prevent many of these complications and allow for a smooth recovery.

What does surgery involve?

You will be asked to come to hospital on the evening or morning prior to your surgery. On arrival you will have your blood pressure, pulse, oxygen saturation level and temperature measured. You will be sized for special stockings (TEDS) which are worn to reduce the risks of blood clots in your legs.

The anaesthetist and a member of the surgical team will visit you. They will discuss the proposed anaesthetic and surgery with you again. You will have the opportunity to ask any further questions. You will be asked to sign a consent form for the proposed operation once you are ready and all your questions have been answered.

Surgery usually takes 1 ½ to 2 hours. You will then be taken to the recovery room, where you will be monitored for about one hour. You will then be taken to your room on the ward.

When you awaken you will find you leg is firmly wrapped and you may have a small drain. The drain is to remove any bleeding from the knee; it usually comes out after 24-48hrs on the ward. A drip will be in your arm. The drip makes up for the lost fluid, which may have occurred in your operation and is used to dispense blood or drugs that you may require. The drip is usually removed 48 hours after surgery. You will be given regular pain relief by the nursing staff in the form of an injection or tablet as required. (See section on pain relief following surgery) You may also have a urinary catheter which will remain until you are more mobile.

The recovery from the operation requires about 4-5 days in hospital for a TKR and 2-3 days for a UKR. In this time, usually the day after surgery you will commence your rehabilitation with physiotherapy. This involves exercises to improve the strength of the muscles and to regain the range of motion of the knee. On the day after surgery your physiotherapist will begin to assist you to get out of bed and walk a small distance. This will be progressed over the next few days, until you are independently mobile.

The exercising and mobilising of the knee will cause some discomfort and swelling, this is normal, and is just part of the healing process. Any swelling and discomfort in the calf muscle should be brought to the attention of the nursing staff as you may require further investigations for this.

After Your Knee Replacement

The post-surgery rehabilitation guide has been designed to enable you to start your rehabilitation in hospital and continue at home. Your physiotherapist will work through this information with you prior to discharge and will be happy to answer any queries.