Knee Replacement: Types, Indications, Contra-indications, Procedure and Complications
Knee replacement is surgical procedure in which the diseased cartilage of the knee joint is removed and in its place a implant made of steel and high density plastic is fixed to the bones.
The surgery of knee joint replacement was first started in the 1940s. These early replacements were a failure. Poor design, inferior quality of implants and a lack of proper understanding of the mechanism of knee joint motion contributed to the development of complications. This situation persisted for thirty years. Only in the 1970s did the first successful design of the knee joint replacement implant come out.
Before reading further it would be a good idea to see the page on knee joint anatomy, to get a better understanding on knee joint replacement. Skip if you have already done so.
There are four knee designs available today for knee replacement surgery. These are
- Partially constrained
- Constrained or the hinge knee
- Unicondylar knee
In the un-constrained type of knee design the femoral and the tibial components are not connected to each other and the stability of the knee joint is dependent on the persons own ligaments. Such a knee is used when the surgeon feels that the ligaments of the knee joint are strong enough to support the knee after surgery.
In the partially constrained type the movement of the tibial and the femoral components is guided by a peg like structure of the tibial component called cam. This also provides some stability to the artificial knee. This implant is used when the posterior cruciate ligament is sacrificed during surgery.
In the constrained or hinged knee the tibial and the femoral components are attached to each other with a hinge like joint.
The uni-condylar knee is used in arthritis of the knee joint that involves only one compartment and the damaged cartilage of that compartment is replaced with the artificial joint.
This is a x ray of a knee replacement with a un-constrained implant.
This is a x ray of a knee replacement with a partially constrained implant. You can see the cam extending from the tibial to the femoral component.
This is a uni-condylar knee replacement. Only on side of the knee has been operated on.
The only indication for knee replacement is osteoarthritis of the knee joint. In this condition it provides relief from pain. The arthritis can be a primary type that is due to the natural wear and tear of the cartilage or a secondary type occurring due to trauma, infection, rheumatoid arthritis, haemophilia, etc.
Knee joint replacement should only be under taken when the pain of osteoarthritis is such that
- it is present even at rest
- night pain is present
- pain is not relieved by analgesics or the patient is fed up of taking analgesics
- there is great difficulty in carrying out activities of daily living
- all other non-surgical methods of treatment have been tried and still there is no significant relief
- and the life expectancy of the patient is 10 to 15 years after surgery
Knee replacement can be done in younger people who are suffering from arthritis involving multiple joints as these people usually have limited activities. But they should be made aware that the implant has a certain lifespan.
Contra-indications or conditions in which knee replacement should not be done include the following
- infection in the knee joint
- persistent infection else where in the body such as a urinary or ear infection
- vascular insufficiency in the limb
- muscular paralysis
- sensory loss in the limb
- a painless but fused knee joint created by surgery done in the past
Before under going knee replacement surgery your doctor will see and document the following things
- he will assess the degree of disability by enquiring about the activities of daily living including activities requiring bending on the knee joint
- the requirement of a walking aid
- examine the knee for stability by checking the integrity of the knee ligaments
- look for any previous surgery around the knee
- measure the degree of movement in the knee and the presence of deformities
- he will exclude other causes of knee pain such as arthritis of the hip and pain due to vascular or neurological causes
- will look for muscular weakness, sensory loss and palpate the pulses in the limb
- ask about the presence of any systemic disease such as diabetes mellitus, hypertension, liver disease etc
- inquire about any addiction such as smoking or alcoholism
Investigations that will be under taken include the following
- Complete blood count
- renal function tests
- liver function tests
- urine analysis
- assessment of cardiac and respiratory function by a specialist or through tests
- x rays of both the lower limbs in standing position including the hip and the ankle joint, taken in two planes
Anaesthesia used is of two types
- General anaesthesia
- Regional anaesthesia
The choice of anaesthesia depends on the patient, the surgeon and the anaesthesiologist. Regional epidural anaesthesia is preferable because it can provide pain relief for up to 72 hours after surgery. This results in less use of morphine based drugs for post-operative pain control.
After anaesthesia a inflatable tourniquet is applied on the upper thigh to control blood loss during surgery. The limb is scrubbed clean, painted with ethyl or isopropyl alcohol and povidone iodine. Now sterile drapes placed about the knee and the surgery is started. A brief summary of the surgery is given below
- A incision is applied in the front to expose the knee joint. After the skin and subcutaneous tissue have been cut, a sheet of tissue is exposed that is the extensor aponeurosis of the quadriceps muscle, along with the patella bone in its centre
- This is then cut along the inner border of the patella, leaving enough margin of tissue to reattach it with stitches later on at the completion of surgery.
- The patella along with the aponeurosis is reflected side ways to expose the cartilage covered condyles of the femur and the tibia.
- The bone spurs, anterior cruciate ligament and menisci are removed.
- Bone cuts are made in the femur and tibial condyles for the attachment of the knee implant.
- A trial implant is now inserted and the movement and stability is assessed.
- At this juncture, if required then contracted ligaments are released.
- If the patellar cartilage is diseased then it is also resurfaced.
- Now the final components are inserted with or without cement depending on which type of implant is being used.
- The tourniquet is now deflated and bleeding vessels are coagulated.
- A suction drain is put to remove collected blood and the wound is closed in layers
- After the dressing the blood circulation in the foot is checked.
Now the operated person is shifted to a post-operative care ward. Vital signs are monitored and kept stable. Here, he or she is kept for 24 hours. The drain is removed after 24 to 36 hours.
Movement of the limb is started on a continuous passive motion machine. Physiotherapy and exercises are begun as soon as pain is tolerable.
Complications can be of two types
- Popliteal artery thrombosis
- Nerve injury
- Fracture of femur bone
- Loss of knee movement due to fibrous tissue formation
Thromboembolism is the formation of blood clots in the veins of the lower limbs, their subsequent dislodgement, migration with blood and their obstruction of the pulmonary arteries that take blood to the lungs. This is a potential fatal complication with a reported incidence of 0.1 to 1%. It is more frequently seen in the following conditions
- female sex
- age above 40 years
- diabetes mellitus
- vascular heart disease
- previous thrombosis episodes
Many methods are used to prevent this complication which include
- compression stockings
- foot pumps
- anti-coagulant drugs such as low dose warfarin, low molecular weight heparin and aspirin
Infection is another important complication that can occur. The incidence is less than 1%. Infection can be prevented by
- Good cleaning and disinfection of the operation theatre with the use of formalin fumigation, UV light and vertical laminar air flow.
- Keeping the operation theatre personnel as minimum as possible and preventing their movement in and out of the theatre.
- Using prophylactic antibiotics.
- Fast and precise surgical technique
More chances of infection are present in persons who have the following conditions
- Diabetes Mellitus
- Low grade persistent infection such as ear infection or urinary infection
- Previous surgery on the knee joint
- Renal failure
- Skin diseases such psoriasis
- are Smokers
A very rare and devastating complication is the formation of a clot in the popliteal artery resulting in gangrene and amputation of the limb. This complication is seen more where there is pre-existing vascular disease. In such patients a use of a tourniquet should be avoided.
Nerve injury resulting in foot drop can also occur following knee replacement. It is usually seen in persons with severely deformed knees. Recovery occurs spontaneously in about half these nerve palsies. In the remaining half partial recovery takes place.
Fracture of the femur can also occur. This is seen if the bone is damaged during surgery and in osteoporosis. Treatment is by stabilization of the fracture with a plate and screws or repeat knee replacement. Fractures of the tibia are very rare.
Loosening of the implant is seen in 5 to 10% of knee replacements after 10 to 15 years. It occurs due to the absorption of the bone around the artificial knee. The cause of this loosening is not clear but it is thought to occur from the release of plastic debris from the tibial component of the artificial knee. Treatment is by bone grafting and repeat knee joint replacement.
Loss of movement can also occur due to the formation of fibrous tissue with in the joint. Treatment is by anti-inflammatory medication and physiotherapy. Manipulation under anaesthesia may also be done. In extreme cases surgery may be required to remove the scar tissue.
Frequently Asked Questions
How long does if take to fully recover from knee replacement surgery?
Full recovery can take up to 4 months while but you can minimise the duration by doing a intensive physiotherapy at home or at a physiotherapy centre.
What can be done to enhance the life of the artificial knee?
Best way to increase the longevity of the artificial knee is to minimise the intensity of load that acts across it by
- reduce weight if you are over weight or obese
- avoid jumping, running and climbing too many stairs
- prevent or treat osteoporosis
I hope the information provided was helpful. If you have any query you can ask me at the contact me page.
This page was last updated on 7th February 2011.
Causes of knee pain include...
Tibial Plateau Fracture
Osgood Schlatter Disease
Go back to Knee Pain from Knee Replacement