A total knee replacement is a surgical procedure used to treat arthritis of the knee. It involves replacing the weight-bearing surfaces of the knee with metal and plastic parts. It is done to relieve pain and improve function of a knee affected with arthritis.
The knee is a complex joint that forms the junction of the thighbone (femur), the shinbone (tibia) and the kneecap (patella). Within the joint, the surface of the bones are covered in articular cartilage. In addition to the cartilage that lines the bone, the femur and tibia are separated by two rubbery cartilage discs known as the menisci. These create additional cushioning between the bones. The bones are held in the joint by ligaments, tendons and muscles.
The most common reason to require a total knee replacement is to treat arthritis of the knee. Arthritis is the term used to describe conditions that cause inflammation in joints. Inflammation leads to damage and destruction to the bones, cartilage and ligaments of the joint. Common causes of arthritis include:
- Osteoarthritis – A gradual wearing away of the articular cartilage and menisci in the knee joint that causes pain and swelling that results in a reduction of movement.
- Rheumatoid arthritis – an autoimmune disease that causes inflammation of the fluid membrane between the bones resulting in excess fluid being produced in the knee joint that leads to pain and swelling.
- Post traumatic arthritis – arthritis that may result following a fracture, dislocation or injury that causes pain and swelling.
When the knee joint is affected by arthritis, it often leads to pain and stiffness. This can result in a loss of movement and difficulty in performing usual daily activities. Pain can occur with activity or with rest. Pain at night often indicates that the arthritis is more severe. Other symptoms that can be experienced with arthritis include:
- Locking, catching or giving way of the knee
- Difficultly going up and down stairs
- Difficulty getting up off the floor, out of a low chair or your car.
A total knee replacement is a surgical option for patients with chronic knee conditions that can no longer be treated effectively with non-surgical treatment.
The procedure involves making an incision to expose the knee joint. The damaged bone and cartilage surfaces are precisely removed from the ends of the femur and tibia. The surfaces of the joint are then replaced with an artificial joint (prosthesis). The prosthesis is made up of several parts:
- The femoral component is a metal implant that replicates the base of the femur
- The tibial component is a metal implant that replicates the top of the tibia
- A plastic spacer separates the two metal components and acts as the cartilage to create a smooth platform for the femoral and tibial components to move on. The plastic is a specialised and treated plastic (polyethylene) that makes it very hard and resistant to wearing out.
- In some cases the cartilage surface of the of the knee cap (patella) is removed and covered in a plastic lining to created smooth gliding when bending and straightening the knee.
A total knee replacement is generally recommended when non-surgical treatment is no longer effective in managing your pain and inflammation and you have increasing difficulty managing daily tasks.
Your doctor will ask you questions about your symptoms and your medical history. A physical assessment will also be conducted to assess your level of knee movement, joint stiffness and stability. Your doctor may also examine your hip and back as it is not uncommon for symptoms from these areas to refer to your knees.
You will be referred for an x-ray of your knees. An MRI and/or CT scan may be required to further evaluate your individual condition.
Total knee replacement surgery can improve quality of life through the following benefits:
- Reduction or elimination of pain
- Increased mobility and movement
- Increases length strength
- Enables you to sleep without pain
- Ability to return to normal activities
- Rectifies deformity (bowleg or knock knee)
As with any surgery there are associated risks to a total knee replacement. The general complications of any surgery include:
- Deep vein thrombosis (blood clot knee) or pulmonary embolism (blood clot lungs)
- Blood loss requiring transfusion
- Heart attack, strokes, kidney failure, pneumonia, bladder infections
- Complication from nerve blocks such as infection or nerve damage
- Anaesthetic complications
The complications specific to knee surgery include:
- Damage to nerves or blood vessels
- Wound irritation or breakdown, numbness and tenderness around the wound and/or difficulty kneeling
- Patella instability (kneecap can move out of place)
- Failure to relieve pain
- Fracture of the knee bones
- Wear of the new joint and revision surgery
- Stiffness in the knee, requiring a manipulation or further surgery
Preparing for your total knee replacement
Preparation begins prior to your admission to hospital. Your surgeon will discuss your surgery and what to expect.
Arrangements should be made in advance to prepare for your recovery including:
- Ensuring your home is free from tripping hazards,
- Ensuring regularly used items are easily accessible,
- Arranging to have someone at home with you or to check in on you when you are discharged.
- A referral to the pre-admission service at the hospital you are having your surgery at can be very useful in helping you plan your transition home following your hospital stay
Your surgeon may refer you to have:
- Routine blood tests and other investigations prior to your surgery.
- A pre-rehabilitation physiotherapy review to ensure you are as fit as possible prior to your surgery
- A review by peri-operative physician, if you have medical problems that need to be managed around the time of your surgery
You will be given instructions regarding your medications and it is important you follow these. These may include:
- Cease blood thinning medication such as aspirin and anti-inflammatory medications up to 10 days prior to your surgery
- Cease naturopathic or herbal medications 10 days prior to your surgery
- Ceasing certain medications used to treat inflammatory arthritis such as Rheumatoid arthritis
Certain lifestyle risk factors can slow your healing following your surgery. In preparation for your recovery aim to:
- Eat healthy
- Quit smoking
- Limit alcohol intake
- Reduce weight if overweight (follow medical advice on safe exercise prior to and following surgery)
Remember to bring your x-rays with you to hospital.
Following your surgery, you will usually remain in hospital for 3-5 days. In this time, you may require antibiotics and pain relief. A physiotherapist will start you moving and help you with post-operative exercises as soon as you are assessed as being safe to move, which in most cases is the day of the surgery. It is important you follow the instructions of the physiotherapist to ensure you get the best out of your new knee.
You will need to use a walking aid initially following the surgery. Once you are assessed as safe, you can also stop using this.
On discharge, you will be given an appointment to see your surgeon as an outpatient. You will also need to continue physiotherapy as instructed.
Recovering from knee replacement surgery takes time, patience and commitment. You will often start noticing rapid improvement in mobility, comfort and ability to perform normal daily actives around 4-12 weeks. You will, however, continue to improve following your surgery up to and beyond 12 months.
- Sutures are usually dissolvable but if not will need to be removed 10-14 days after surgery.
- Your dressing is water proof and allows you to shower as usual. Your surgeon may have some particular instructions about your wound care. You will generally see your surgeon at 10-14 days post operatively to review your wound and remove your dressing.
- Avoid rubbing creams or lotions on your leg until you have discussed this with your surgeon
- Driving can be recommenced following discussion with your surgeon. For total knee replacement surgery it is around 6 weeks after surgery.
- Hydrotherapy should not commence before 4 weeks, or after your surgeon tells you so.
- If you are having procedures such as dental work or other surgery, you should consult your surgeon who may recommend you take antibiotics before and after your procedure to prevent infection in your new prosthesis. All non essential dental work should be avoided for 3 months following your new joint replacement.
- Your new prosthesis may cause the metal detector to alarm at airports. A letter from your surgeon is generally not required prior to travel.
- Your surgeon will continue to follow your progress and how you and your new joint is functioning as time passes. Regular reviews and X-rays will be performed to ensure that you preforming well.