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.
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.
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.
Knee Replacement Videos
Knee replacement Surgery in 2020- 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.
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 a couple of 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.
Advances in Knee Replacement Surgery
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.
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.