Knee Replacement

As with hip replacements, Knee replacement procedure is the definitive treatment for severe arthritis of the knee joint causing symptoms that are intrusive in a person’s day to day life and not adequately controlled by non-surgical means.

Commonly, these symptoms include pain at rest, pain at night, pain with activity, stairs, inclines/declines, swelling, sometimes a subjective sensation of giving way, legs becoming more bow legged or knock kneed.

Like hip replacements, knee replacement surgery has also come a long way and whilst they are however major operations with inherent risks, results today are very pleasing with high patient satisfaction due to restoration of function through alleviation of pain.

The Procedure

In a Knee Replacement, the knee joint is accessed through an incision on the front of the knee. The arthritic parts of the Femur (thigh bone), Tibia (shin bone) and often the Patella (knee cap) are shaved off and replaced by the prosthesis.

Materials Used

The artificial Knee Prosthesis comprises of a metal femoral component, a metal tibial component, a plastic insert between the two and a plastic button for the knee cap. The femoral and tibial component are fitted onto the respective bones like a ‘crown on a tooth’, often with cement. The insert clips in between and the movement happens between the femoral component and the plastic insert. Unlike Hip Replacements, the bearing surface in Knee replacements are uniformly Metal on Plastic.

Recovery

The operation is performed under a general or a spinal anaesthetic. Depending on the time of the operation, the patients are up walking (with a frame) the same day or the next day. Patients often stay 1-3 days in hospital and then may spend a week or so in a rehabilitation hospital where the focus is on physiotherapy. Alternatively, patients may get discharged home directly and see a physiotherapist in the community few times a week. There are no hard and fast rules about this as long as one works hard the first month to restore your movement range and strength. Return to work would depend on the type of work being undertaken but for most occupations this can be expected by 6-8 weeks.

Unlike hip replacements though, Knee replacement require significantly more motivation and effort on the part of the patient, especially in the first month after surgery. Patient motivation in rehabilitation has been identified as the single most important factor in getting a good result.

Overall recovery may take a year (till all healing comes to a plateau) but functional recovery can be expected by 4- 6 weeks. Some aching pain and swelling can remain for many months but as long as everything is gradually improving, this is all expected. These symptoms often wash away over 6-12 months.

Longevity

knee-replacement-longevity Modern joint can often be expected to last a couple of decades. Patients can expect to get back to most if not all of their pre-operative or sometimes even pre-arthritis activities.

Activities such as bush walking, cycling, swimming, bowling, yoga, even doubles tennis are all common things people can go back to after joint replacement surgery. Some people may find kneeling uncomfortable.

Impact activities such as running, jogging, jumping though, are not recommended as they could compromise longevity.

When to consider a Knee Replacement?

knee-replacement-needed There is no such thing as “you need a hip or knee replacement!”. Need is something the patient determines and should be guided strictly and only by the patient’s level of symptoms and after non operative measures have been exhausted.

If surgery is delayed, apart for the symptoms, the patient is unlikely to be disadvantaging themselves in terms of outcome of their operation.

In Australia in today, it would be extremely unlikely that someone ‘will end up in a wheelchair’ if they delayed their operation.

Knee replacement Surgery in 2023- Advances, expectations and recovery

Knee replacements have been constantly evolving over the last half a century. Initial designs used a simple hinge mechanism which went through many modification with current modern designs boasting ultra-congruent designs and medial pivots that attempt to mimic the natural knee closely as much as possible. Biomaterial advances have led to better metal compositions and finishes as well as improvements in the polyethylene insert, the artificial cartilage substitute, to make it more resilient. Other advances such as patient specific (custom instrumentation) and Robotic Assisted Knee replacements are discussed below.

Customised implants

In 2022, customised knee replacement implants were introduced in Australia. These are at very early stages of its introduction and whilst making some parts of the surgery a bit easier, at this point have not shown any measurable patient outcome difference. They do require a fair bit of preparation and therefore are not in routine use. If you would like to know more about them, please let us know and we will be happy to discuss more, including your suitability for this option.

Expectation of a successful knee replacement is a pain free knee that allows a patient to function in their day to day life. Remember, the patient that has a knee replacement is often unable to attend to day to day activity due to pain prior to their operation. As such, expectations must be realistic. This is not as good as the knee we are born with and whilst the aim is to get as close to what the knee was like prior to the disease set in, it will never be what the natural knee was like. IT WILL HAVE SOME LIMITATIONS. We all hope that we don’t find these limits during the course of our activities! Having said that, we do have patients that have climbed Mt Kilimanjaro after their knee replacement but for most, the disabling pin of arthritis is gone, they are much more mobile, agile and functional.

Recovery is influenced by a multitude of factors but initial functional recovery is expected to be fairly quick. Patients are usually up walking with a frame or crutches a few hours after their operation. They may leave hospital as soon as they are safe on crutches / stairs and this is usually anywhere between 1-4 days, often a couple of days.

One of the most important factors in determining outcomes is how motivated and proactive the rehabilitation is. This is directed by the patient. Going to a rehab facility and spending a week or two there after the hospital or going straight home or to an outpatient facility a few times a week or the local physio are all options and there is no right or wrong as long as the patient is motivated and proactive with their exercises (within what has been prescribed). This is to recover the movement before scar tissue forms and stiffens the knee which can negatively affect the outcome.

Patients are expected to have some discomfort or even pain for many months that continues to improve every day. The ‘healing process’ though, may continue for a couple of years. Sometimes this can manifest itself by a feeling of discomfort or tightness in the knee.

‘Clicking’ in a knee replacement is quite normal. Often patients get used to it and it becomes less noticeable. Very occasionally, it may be a problem such as new onset clicking.

The following videos are aimed at showing you what most patients mobility is like at different times after their operation.

Knee Replacement Videos

Advances in Knee Replacement Surgery

Computer Navigation

Computer Navigation has been routinely used in Knee Surgery for over a decade. This technology utilizes 3 point positioning systems with the assistance of infrared lights and gate detectors to guide the surgeon. The aim is to improve our ability to recreate normal alignment thereby optimizing outcomes of the operation. Whilst the technical side of this has certainly improved, navigation thus far has not been shown to make a difference to long term outcomes.

Patient Specific Instrumentation

Patient Specific Instrumentation (PSI) is often erroneously believed to be custom implants. The Implants are NOT custom made for individual patients. The instrumentation used for the procedure (cutting blocks) are custom made for the individual patient. Often a CT or MRI scan is taken weeks before surgery and based on information from these, certain instrumentation is produced to assist with the surgery. This does reduce the number of tools required in surgery and may also improve implant positioning. Again, PSI technology thus far has not shown to make a difference to long term outcomes.

Robotic Assisted Knee Surgery

This is has opened the most recent frontier in the treatment of Arthritis. Robotic Technology in Joint Replacement comes in various forms. Once again, the aim is to improve our ability to recreate the Knee Joint mechanics as close to what they were before being affected by arthritis. Robotic assisted surgery certainly shows a lot of promise and changing at a rapid pace. Difference in results are yet to be seen.

Lower Limb Realignment (High Tibial Osteotomy)

For people who are suffering with arthritis but are too young and high demand to consider a Knee Replacement, a Realignment of the knee can be considered. The purpose of this is to unload the diseased part in order to delay the need for a Knee Replacement.

Here’s How It Works

Arthritis can commonly affect the inner (medial) aspect of the Knee joint.

Loss of cartilage in this part means the knee may become a little bow legged thereby increasing load and a cycle of ongoing damage begins.

In this situation, making the knee a little knock kneed may unload the inner diseased aspect of the joint.

Realignment is a ‘time buying’ procedure. It does not cure the arthritis but simply alleviate symptoms by unloading the overloaded part of the joint. The wear and tear will continue until a Knee replacement is finally required, but by delaying the need for it, patients can return to an active lifestyle with less or no pain for a long time.

Realignment Osteotomy is a major operation and can take a long time to recover. It usually requires patients to be on crutches for about 6 weeks and need physiotherapy for around 3 months.

A successful realignment has been shown in the literature to avert knee replacement surgery for over a decade.

Patellar Realignment

The Patella or ‘Knee Cap’, is a small bone that the quad muscles attach to. The Patella in turn attaches to the Patellar Tendon that connects the Patella to the Tibia (Shin bone). This way the quad muscles exert a pull on the shin bone to straighten the Knee Joint.

Its purpose is to improve the mechanical advantage of the quad muscles, similar to the way a ‘pulley’ works.

The back of the Patella has cartilage (polished surface) and it articulates with the front of the Femur (thigh bone). This part of the Knee joint is known as the Patellofemoral joint.

As seen in cross section, The Patella rests in a grove on the front of the Femur (known as the ‘Trochlea’) and moves up and down in the middle of this grove with straightening and bending of the Knee.

There are many factors that maintain the Patella (Knee Cap) balanced and stable, tracking centrally in the middle of this Trochlea (Femoral grove) as it moves up and down during bending and straightening of the Knee joint. Conditions that affect any or many of these stabilizing factors can alter this balance leading to an abnormal tendency towards pushing the Patella Laterally (outwards). This abnormal movement is known as ‘Maltracking’.

Consequences of Patellar Maltracking

Patellar Maltracking can cause problems ranging from instability (Knee Cap popping out) on one hand, to an increased pressure behind the patella causing pain often referred to as ‘Anterior Knee Pain’ on the other. Whilst instability or Patellar dislocation can cause major cartilage damage even in one instance, these pressure changes cause slower early wear of the cartilage surface (Chondromalacia Patellae).

All of these culminate in ongoing damage to the cartilage i.e., Arthritis.

Treatment of Patellar Maltracking

Physiotherapy

Initial treatment in most cases is Physiotherapy and Bracing or Taping. The aim here is to loosen tight structures that exert an outward pull on the Knee Cap and strengthen the ones that pull the Knee Cap inwards. Physiotherapy regime focused on VMO (inner quads) strengthening and ITB stretches is commonly prescribed. This in combination with Taping is often successful in improving symptoms.

Deep squats, lunges and any deep flexion (extreme bending) of the Knee Joint should also be avoided as these particular movements overload the Patellofemoral joint causing pain.

In the vast majority of cases, these non- operative options will suffice in controlling symptoms.

Surgery

Realignment surgery of the Patella refers to procedures that correct that imbalance between a tighter outer pull and a weaker inner pull. This is needed when symptoms cannot be controlled with simpler non-operative measures.

The exact nature or realignment depends on the type of malalignment but generally speaking, it either entails:

A soft tissue procedure whereby the inner structures are tightened (Medial Plication) or stretched/torn ligaments (MPFL) reconstructed and tighter outer structures loosened by releasing them (Lateral release).

A soft tissue procedure combined with a bony procedure whereby abnormal shape of Tibial Tuberosity part of the Tibia (Shin bone) is corrected by repositioning it. There are various ways of doing a bony correction. Associate Professor Qurashi performs the Fulkerson’s Procedure when required. This procedure is a major operation and does require a lengthy period of rehabilitation. The hospital stay is usually only overnight but patients are often on crutches and in a brace for 6 weeks (but mobile and often functional for office/desk type duties) and it takes another 4 weeks or so to learn to walk normally. Whilst a Patellar Realignment does not cure Arthritis, it can slow down the progression of Arthritis by improving the alignment and alleviate symptoms.

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