TOTAL KNEE REPLACEMENT
The knee joint is the articulation between three bones: the thigh bone (femur), the larger of the two bones in the leg (tibia) and the knee cap (patella). The joint surfaces are covered with a special lining called ‘articular cartilage’ which allows smooth gliding of the joint surfaces.
Arthritis develops when the lining gets damaged due to various reasons including ‘wear and tear’, inflammation (like rheumatoid arthritis). The knee becomes painful and swollen. The initial management is non-
When the pain due to knee arthritis increases and is not controlled by conservative measures, then it would be appropriate to consider surgical options. While partial knee replacements can be considered in selected patients, in majority of the patients most of the knee is affected by arthritis which would require a total knee replacement.
During total knee replacement, the surgeon resurfaces the knee joint with an artificial joint containing metal and plastic component. In majority of the cases, the metal components are fixed to the bone with bone cement.
While knee replacement is one of the most successful operation and in majority of patients there is a good functional outcome, it is important to understand that the aim of a knee replacement is to improve pain and function. It does not make the knee to go back to the status of a normal knee. In general, a flexion (bending of the knee) of between 100 to 120 degrees is expected following a knee replacement, the range of movement achieved often depends on the preoperative stiffness.
There must be a realistic expectation by the patient about what the operation can achieve and, whilst in majority of the patients there is good pain relief, studies have shown that a proportion of patients may still have some residual discomfort in the knee even when the knee replacement is technically successful. It is unlikely that high level of athletic activities would be possible (and probably not advisable) and in particular some high impact sports should be excluded. It is also likely that some of the activities like kneeling, squatting etc., probably would be limited in majority of the patients.
Like any major operation it has certain risks (although rare) including that of infection, bleeding, damage to the neurovascular structures, thrombo embolism (clots in the legs which can go to the lungs), stiffness, anaesthetic complications etc., (see section on complication). The complication rate will be somewhat higher if the knee replacement is more complex (see revision knee replacement). The complication rate to some extent will also depend on the individual patient’s medical status and Mr. Ganapathi will in some cases ask for an anaesthetic opinion before deciding on surgical treatment.
Example of a complex knee replacement:
rays of the right knee an elderly patient with comminuted fracture of the distal femur (thigh bone) with pre- existing symptomatic arthritis
CT scan picture showing the gross arthritis and the multi-
fragmented and intra- articualr nature of the fracture.
3D CT scan demonstrating the fracture pattern
The nature of the fracture and the pre-
rays at 4 ½ months showing that the fracture is healing
Function at 4 ½ months post surgery
What type of anaesthesia will I have?
The anaesthetist will discuss with you regarding the different types of anaesthesia (spinal or general). To decrease the postoperative pain, Mr.Ganapathi routinely inject the operated area with local anaesthetic which has been shown to decrease the use of painkillers which can make you drowsy and delay rehabilitation.
How long will I stay in the hospital?
The length of stay varies depending on the individual factor. While on average it would be about 3-
In suitable patients, knee replacement could be performed with muscle sparing approach. While, it is unlikely that there is long term functional advantage, some studies have shown short term functional advantage.
What is the rehabilitation period?
Most patients start physiotherapy soon after surgery. A frame, crutches or a stick may be needed for up to 6 weeks and older patients may have to continue the use of a walking aid for longer periods. The physiotherapist will guide you through the exercises. You may take up to between six and twelve weeks off from work depending on the job you do. In some patients, it may be appropriate to consider moving to a lighter job.
What restrictions will I have?
Majority of patients who undergo knee replacement experience a good reduction in the pain and improvement in functional activities. Patients are encouraged to resume an active lifestyle. However, it is advisable to avoid activities that produce high impact such as running and jumping. Sports such as golf, cycling, swimming and walking are encouraged.
Can I have bilateral knee replacements in the same sitting?
Often knee arthritis involves both knees. While in general it would be appropriate to replace the worst affected knee first followed by the second side few months later, it would be certainly possible to do replacements of both knees in the same sitting. However, this would depend on the severity of the arthritis as well as the individual patient circumstances including medical fitness for surgery. Mr.Ganapathi would be happy to discuss those issues during the consultation.
What do I do to optimize myself before surgery?
Before the surgery, it is important that any medical problems (like high blood pressure, diabetes) which you may have are under control.
If you are overweight, you should try to reduce the weight as studies have shown that the complication rates are somewhat higher in overweight patients undergoing knee replacement.
Infection following a knee replacement is very rare. However, to decrease the risk of infection any foci of infection should be treated before surgery. If you have any skin infection it is important to have that treated before having a hip replacement. Similarly if there is water infection or dental infection this should be treated beforehand.
Smoking increases the complications following major surgery. Cessation of smoking even for few weeks prior to surgery has been shown to decrease the complications.
Strategies to improve function and decrease the failure rate following knee replacement
- Improvement in the design of the knee replacement have occurred over the past decade.
- More recently, the plastic component of the knee replacement (the main source of wear related particles leading to loosening) is also being modified (cross linked poly) to improve the wear resistance and it is hoped that this will lead to more durable knee replacements. Mr.Ganapathi uses this type of plastic when performing knee replacement in young and more active persons.
- Many studies have shown that despite the surgeon’s best efforts, there are some patients in whom the knee replacement components are not placed in the optimal position and alignment. This inaccuracy is often is due to the use of conventional manual jigs used to prepare the bones for knee replacement which has a degree of inaccuracy and an element of “eye balling” is often involved. If the components are not placed in optimal alignment and position, in addition to less than optimal functional result, the knee replacement may also fail early due to eccentric wear of the plastic. This is not dissimilar to the car tyres getting damaged early if the tracking and alignment are not correct. More recently, with advances in the computer software it is possible to use computer guidance to cut the bones.