A knee arthroplasty is the medical term used to describe knee replacement surgery. This is an extremely common type of surgery performed in over one hundred and sixty thousand patients annually in the UK. The primary aim of knee arthroplasty surgery is to reduce pain to allow improved walking ability and a better night’s sleep.
In the vast majority of cases knee arthroplasty surgery will need to be considered due to severe pain related to age related changes to the knee known as osteoarthritis.
In a far smaller number of patients a knee arthroplasty will be considered to relieve pain associated with inflammatory joint disease, the most common form being rheumatoid arthritis. Rarely, significant knee trauma such as severe fractures require a knee arthroplasty.
Prior to undergoing a knee arthroplasty at Circle Health you will be invited to a pre-admission clinic. The aim of a pre-admission clinic is to give you the chance to ask any specific questions you have about the surgery with your specialist orthopaedic knee consultant and anaesthetist. Our specialist anaesthetist will also take a more detailed medical history and conduct some tests on your heart and lungs.
General anaesthetics can be conducted in several ways and your anaesthetist may discuss with you on the basis of these tests which general anaesthetic may suit you best. In rare cases, the risks of undergoing a general anaesthetic may be too great due to existing medical conditions affecting the heart, lung or vascular system. In these circumstances, your anaesthetist may offer an alternative to a general anaesthetic known as a spinal anaesthetic which numbs your legs during the operation.
Your specialist knee orthopaedic surgeon may also request up to date x-rays and in some cases more specialist imaging such as CT scans. Sometimes these images can be useful in planning surgery.
Under normal circumstances you will be admitted to Circle Health’s surgical unit on the morning of your surgery.
A knee arthroplasty surgical procedure involves several stages. Before the surgical procedure itself commences your surgical team will position appropriate equipment to monitor vital signs. These will include a blood pressure cuff to monitor blood pressure, ECG leads to monitor the electrical activity of the heart and a monitor to measure oxygen levels.
A tourniquet will be placed around your thigh to reduce the amount of blood loss prior to making the initial incision.
The incision will be made in a central, vertical line across the front of the knee. Once the knee cap (patella) is exposed it is then placed to the side of the knee so the surgeon is able to gain access to the knee itself.
Using accurate cutting tools your surgeon will then initially remove the bottom part of the thigh bone (femur) and re-shape the end of the bone ready to implant the first part of knee prosthesis. Once the femoral component is fitted, sometimes with the use of cement, the surgeon will then remove the damaged tibial (lower leg bone) joint surface and fit the second part of the knee prosthesis.
Once securely in place a strong insert is placed between the two components to reduce the impact of weight bearing and moving the knee during it’s lifespan. Your surgical team will relocate your knee cap to the groove provided by the femoral prosthesis. Prior to stitching the tissues back up your surgeon will ensure the knee is moving through an appropriate range of moving in a smooth fashion.
The entire procedure will normally take between one to two hours and you will be safely woken from the anaesthetic in the comfort of Circle Health’s recovery room with our specialist staff to assist you.
General complications which can occur with any type of invasive surgery can occur in a small number of patients who undergo a knee arthroplasty. These can include:
- Reaction to undergoing a general anaesthetic can be highly variable among individuals. Drowsiness is common and some individuals may experience some nausea and vomiting following surgery.
- A blood clot (deep vein thrombosis - DVT) can occur after surgery due to the reduced time spent being active which normally helps to pump the blood around the legs. Your specialist will often recommend blood thinning (anticoagulant) medication following a knee arthroplasty to help prevent this. Our physiotherapists will also encourage bed and chair exercises to help keep the blood moving in the lower legs.
- In rare cases if a blood clot develops it can travel to the lungs which is known as a pulmonary embolism (PE) or travel to the brain which can be life threatening or cause permanent neurological damage.
- The medication/s used as part of the general anaesthetic reduce the sensation of the nerves and muscles around the bladder which can lead to urinary retention. In a small number of cases individuals may need catheterization for a short period after their surgery until they are able to pass urine properly. For this reason, patients are encouraged to keep well hydrated following a knee arthroplasty.
- Due to general activity being reduced following surgery as well as the effects of some general anaesthesia and pain controlling medication individuals will tend to breath in a shallower pattern. For this reason, patients are encouraged to complete regular breathing exercises to circulate the air in the lungs and prevent chest infections following a knee arthroplasty.
There are also some specific risks associated with a knee arthroplasty operation. These will be discussed in detail with you by your surgeon prior to your operation and can include:
- Patients may suffer with permanent numbness in the side of the knee next to the site of the incision. More significant nerve damage affecting the strength of the muscles or lower down the leg is extremely rare.
- Following a knee arthroplasty, some patients may notice a leg length difference. This may seem more prominent in patients who had significant bowing (in or out) of their knees prior to the surgery.
- The risk of infection is increased with knee arthoplasty surgery compared to more commonly used keyhole operative procedures. However, infection rates are still extremely low and our theatres use air flow systems which results in highly filtered and very rapid changes in air pressure ensuring the environment is as clean as possible. Your specialist will also prescribe antibiotic treatment following your surgery to help reduce the risk of infection.
- In very rare cases the knee replacement itself can fracture the bone which it is inserted in to. This normally occurs during the operation itself.
You will require a short stay in hospital after a knee arthroplasty which is normally in the range of 3-7 days. Depending on your location and your preference you may stay as an inpatient for longer to commence more advanced rehabilitation supervised by your physiotherapy team. Prior to your discharge from hospital your surgeon may request an up to date x-ray to ensure that the placement of the knee prosthesis is correct and there are no early signs of infection.
During your inpatient stay with Circle Health, your vital signs will be monitored by our specialist doctors and nurses. Your pain levels will be monitored throughout your stay and appropriate analgesia will be offered. To reduce the pain and swelling in your knee we will encourage the use of regular icing by way of a device known as a cryocuff which provides an easy to use, shaped bag of iced water to surround the knee joint and soft tissues.
A continual passive motion (CPM) machine will also be offered which provides a supportive brace to place the operated knee while moving the joint gently through an appropriate range of motion. This can be useful to prevent too much post operative stiffness and allow a more rapid transition to movements such as sitting to standing and climbing stairs when appropriate strength has been achieved.
Your rehabilitation will be conducted under the supervision of Circle Health’s expert physiotherapists at all time. Initial rehabilitation following a knee arthroplasty aims to reduce knee stiffness and restore full extension (straightening) and at least ninety degrees of flexion (bend) of the knee. Under normal circumstances your physiotherapist will aim for your knee to have full extension and at least 90 degrees flexion by six weeks after the operation.
In order to achieve this, you will initially be shown gentle exercises to perform regularly to extend and flex your knee as your pain allows. These initial exercises will normally be done in lying so you are able to perform them in bed to prevent excessive knee stiffness developing when resting.
As your pain settles you will be advised to progress to more aggressive stretching exercises and may be shown some positions which you can rest your knee in for prolonged periods of time to increase the flexibility.
Strengthening exercises should also be commenced immediately after a knee arthroplasty. Early in the rehabilitation cycle, the exact type of exercise will be determined by your pain levels and how much activity you are able to get in your quadriceps muscles (thigh muscles).
At Circle Health, our expert orthopaedic physiotherapists will assess this on the ward before you are supervised when mobilizing for the first time after your knee arthroplasty.
Depending on the strength of your knee and your pain levels your physiotherapist will decide whether to issue a walking frame or two elbow crutches. You will be advised as to how best to transfer from lying to sitting over the edge of the bed and then how best to transfer safely in to standing.
Our Circle Health physiotherapists will tutor you on how to safely and effectively use the particular walking aid you have been provided with. On your first few attempts at walking on the ward, you will be supervised at all times.
Following a knee arthroplasty some patients may progress at a slightly slower rate due to pain levels or general factors such as age and pre-operative mobility. Some systemic diseases such as diabetes may also affect the rate of progress. In all cases, our expert physiotherapists at Circle Health will tailor the program according to your individual needs.
Patients are reviewed by their specialist orthopaedic surgeon at ten to fourteen days after their operation. At this appointment the surgeon may request a further xray and will conduct a physical examination of the knee. At this appointment, patients will also see a member of Circle Health’s orthopaedic nursing staff which will examine the wound and extract the staples. All being well, your specialist will communicate with the physiotherapy team who will then be able to review the difficulty of the exercises and progress accordingly.
Progressions of the strengthening exercises will normally involve some light exercising on a static cycle in the gym and progressing exercises to those involving weight bearing. These exercises, known as compound exercises more quickly achieve strength in the operated knee to enable you to walk, sit to stand and climb stairs more effectively. Some examples of these exercises are listed below:
- Sit to stand repeats
- Wall squats
- Low step up
During your rehabilitation, you will be progressed from using a walking frame to elbow crutches and once you feel entirely safe with elbow crutches your physiotherapist will advise you to begin walking with one elbow crutch only. Once you are able to walk with a more equal stride pattern your physiotherapist will assess your walking pattern (gait) and may suggest a walking stick rather than an elbow crutch.
Your Circle Health knee consultant will review your progress at six months following surgery. In some circumstances, they may request some up to date imaging and will again communicate any difficulties to the physiotherapy team. Many individuals are able to progress to walking with no walking aid six months after a knee arthroplasty.