Knee Replacement Surgery
Arthritis of the knee
Knee replacement surgery
Anaesthesia for knee replacement surgery
Possible complications following knee
replacement surgery
Activity following knee
replacement surgery
Arthritis of the knee
The knee
joint is formed by the lower leg bone (shin bone), called the tibia, and the thigh bone,
called the femur. The ends of the bones are covered with a smooth layer of
cartilage. The joint is enclosed by a fibrous tissue envelope or capsule with a
smooth tissue lining called the synovium. The synovium produces fluid that reduces
friction and wear in the joint. Normal joints allow nearly frictionless and
pain-free movement. When the cartilage is damaged or diseased by arthritis, joints become
stiff and painful.
Osteoarthritis
Osteoarthritis is the result of wear and tear on the joint.
The normal cartilage lining is gradually worn away and the underlying bone exposed. It may
be many years before the damage to the joint becomes noticeable. Pain and stiffness are
the usual problems associated with osteoarthritis. The medial (inside) part of the knee is
most commonly affected by osteoarthritis. Previous injury to the knee ligaments or
cartilages (menisci) may predispose to this kind of arthritis. Being overweight may
also increase the likelihood of arthritis, or make it worse.
Inflammation
Inflammation of the joints can be caused by a variety of conditions,
the commonest of which is rheumatoid arthritis. Inflammation causes damage to the
cartilage lining of the joints. This causes arthritis which is often more widespread than
osteoarthritis, and typically affects several joints. This kind of arthritis can affect
people when they are relatively young and may cause severe disability.
Treatment of arthritis
If the arthritis is inflammatory in nature, then a specific diagnosis
should be sought. Blood tests and other tests can help to determine the type of
arthritis involved. Anti-inflammatory and other drugs may be helpful .
For patients with osteoarthritis, it is important to remain flexible
and to maintain as much movement as possible. Analgesics (pain killers) can help
patients to maintain activity. Many modern pain killers also have an anti-inflammatory
effect, which may be beneficial in arthritis.
If arthritis is severe and significantly affects activity, then
surgery may be appropriate.
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Knee Replacement
Surgery
In knee replacement surgery, the damaged bone and cartilage
are replaced with metal and plastic surfaces that are shaped to restore knee
movement and function. The new artificial knee is called a prosthesis.The prosthesis
is generally composed of two metal pieces fitted onto the ends of the tibia
(shin bone) and the femur (thigh bone) and a plastic piece inserted between
them to act as a bearing. Stainless steel, cobalt or chrome alloys or titanium
may be used for these components. Durable, wear resistant polyethylene (plastic)
is used for the bearing. A plastic bone cement may be used to anchor the
prosthesis into the bone. Some joint replacements also can be implanted without
cement when the prosthesis is designed to fit and lock onto the bone directly.
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| Total Knee Replacement prostheses in situ |
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Unicompartmental knee replacement surgery
When only one part of the knee joint is arthritic, it may
be possible to replace just this part of the joint. The procedure is similar to a
total knee replacement, but only one side of the joint is resurfaced. A metal
component is fit onto the femur (thigh bone) and a plastic bearing is inserted either
directly onto the tibia (shin bone) or onto a metal tray which has been fit onto the
tibia. Recovery time is generally slightly shorter following this kind of surgery.
Bilateral knee replacement procedures
Occasionally, the patient and surgeon may decide that
having both knees replaced at the some time is an acceptable option. The benefits are that
the patient only has to come to the hospital one time, have one surgery and one recovery
time. The initial recovery will be slower and physiotherapy will be more difficult at
first. The patient will be in the hospital longer than if only one joint was
replaced. Bilateral knee replacements are not recommended for all
patients. Having both joints replaced at one time requires a
commitment to work twice as hard for a successful outcome, although bilateral
joint arthroplasty has many benefits and is worth the extra work in the initial recovery
period.
High Tibial Osteotomy
Sometimes, if predominantly one side of the knee is arthritic, an
operation may be performed to realign the knee joint in order to take pressure off the
affected side and redistribute weight bearing more onto the other side of the
knee. This operation, called a high tibial osteotomy, involves making a cut in
the tibia (shin bone) and removing a wedge of bone to change the angle of the knee joint.
A staple or plate and screws are used to hold the bone in place until it heals.
Although this procedure is not suitable for all patients, it may produce significant
relief and delay the need for knee replacement surgery.
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Anaesthesia for total knee
replacement surgery
Knee replacement surgery can be performed under general,
spinal or epidural anaesthesia. A combination of techniques is often used.
General anaesthetic
The patient is asleep throughout the procedure. A
breathing machine (ventilator) may be used to assist the patient's breathing during
anaesthesia. Many patients feel drowsy or groggy after a general anaesthetic.
The use of newer anaesthetic drugs has significantly decreased the occurrence of
post-operative nausea and vomiting.
Spinal block or epidural block
These techniques use local anaesthetic to block the passage
of nerve impulses, including pain, in the spinal cord. The block can be positioned
at various spinal levels, but the patient generally has no feeling from the waist
down. The patient is usually sedated during the procedure, but a
ventilator is usually not required for this kind of anaesthetic. It thereby can
lower some of the risks of general anaesthetic. Depending on the medications used for the
block, the period of pain relief after surgery can be prolonged for several hours,
reducing the need for pain medication after surgery. Because these blocks provide
temporary loss of sensation below the waist, a urinary catheter (tube into the bladder to
drain urine) is often inserted.
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Possible
Complications of total knee replacement surgery
Any surgical procedure carries various risks and potential
complications. Although uncommon in joint replacement surgery, the following complications
sometimes occur.
Blood Loss Requiring a Blood Transfusion
In any joint replacement surgery, some blood loss will occur.
Occasionally a blood transfusion may be required. Precautions will be taken during the
operation to minimise blood loss. Some patients may be given the option to donate their
own blood pre-operatively.
Infection
Any surgery performed via an incision in the skin carries the
risk of infection. Many precautions are taken during surgery to minimise the risk of
infection. Intravenous antibiotics are usually given during surgery to help
prevent infection. The operating room is also equipped with special air flow devices that
minimise bacteria in the air.
Blood Clotting in the Legs (Deep Venous Thrombosis
(DVT))
The circulation to the legs may be decreased during knee
replacement surgery due to immobilisation of the legs. Decreased movement of blood through
the veins (venous stasis) can cause the blood to clot. Blood thinning medication is
used to help minimise this risk, but a small percentage of patients
still develop blood clots in the leg.
Blood Clot Moving to the Lungs (Pulmonary Embolism
(P.E.))
Occasionally, blood clots that form in the legs may become
detached and travel to the circulation in the lungs. This complication, although extremely
rare, can be life threatening. Symptoms include chest pain and shortness of breath.
Nerve Injury
Any incision can result in damage to the sensory nerves in the
area of the incision. Significant nerve damage, which may cause loss of muscle function,
can occur after knee replacement.
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Activity
after a Knee Replacement
Very few restrictions to activity are required following
knee replacement surgery. It is extremely important to move and exercise the knee
early in the postoperative period in order to regain the best range of movement possible.
Physiotherapy will usually be commenced on the first postoperative day, or on the day of
the operation. If the joint is not moved early on, it will become stiff and have a
decreased range of movement, which will limit the utility of the new knee.
Recovery time after a Knee Replacement
By the time patients are discharged, they should be able to
get in and out of bed and walk to the bathroom.
Most patients are around 80% recovered by six weeks
after surgery. They will continue to improve more gradually over the next three to six
months. Recovery varies from person to person depending on their level of pain and
activity before their surgery.
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