A partial knee replacement is a surgical procedure used to treat arthritis of the knee. Unlike a total knee replacement, only a small part of the knee is replaced with an artificial joint (prosthesis).
The knee is made up of three compartments:
- The medial compartment, located on the inner side of the knee
- The lateral compartment, located on the outer side of the knee
- The patellofemoral compartment, formed by the knee cap and part of the femur
A partial knee replacement involves replacing only one or two of the compartments. Approximately 10-15% of patients with knee arthritis will have their arthritis limited to one or two compartments of their knee. Common conditions leading to this type of arthritis are:
- Osteoarthritis: Early disease is often seen in omg one or two compartments
- Post Traumatic Arthritis: An injury can cause damage to the cartilage in one compartment
- Abnormal alignment of the knee
- Meniscal injury and previous meniscal surgery
When only part of the knee is affected, it is common to experience symptoms limited to that affected area. If one (or two) compartments are affected and symptoms are related to those areas, you may be a candidate for a partial knee (uni-compartmental or bi-compartmental) knee replacement.
A partial knee replacement is a surgical option for patients with chronic knee pain and disability that can no longer be treated effectively with non-surgical treatments.
Your doctor will ask you questions about your symptoms and your medical history. Some medical conditions and/or a previous history of knee ligament injuries may mean you are not a candidate for a partial knee replacement.
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 to confirm that only part of your knee is affected. An MRI and/or CT scan can also be very useful to help decide if you are a candidate for a partial knee replacement.
The procedure involves making an incision to expose the knee joint and precisely removing only the damaged segment of femur, tibia and meniscus cartilage. These damaged bone ends are then replaced with metal components. A plastic spacer replicates the damaged segment of cartilage and meniscus. Unlike a total knee replacement, your ligaments are left completely intact.
Partial Knee Replacement surgery can improve your quality of life and has the following potential benefits:
- Smaller surgical incision over the knee
- Less blood loss during surgery
- Quicker recovery
- Less painful than total knee replacement
- Shorter hospital stay
- Better movement of the knee
- Feels more like a normal knee
- Good for elderly people who may not tolerate a larger surgery.
As only part of you knee is replaced, there is the possibility that arthritis could develop in the remaining part of your knee over time, so a further operation in the future may be required.
As with any surgery there are associated risks to a partial knee replacement. The general complications of any surgery include:
- Deep vein thrombosis (blood clot legs) or pulmonary embolus (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 including nausea and vomiting
The complications specific to knee surgery include:
- Damage to nerves or blood vessels
- Wound irritation or breakdown
- Patella instability (kneecap can move out of place)
- Failure to relieve pain
- Revision surgery required for wear of the new artificial joint or development of arthritis in other compartments in the knee
- Stiffness in the knee
- Numbness and tenderness around your wound and difficulty kneeling
Preparing for your Partial 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 discharge 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.
- Cease 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 your 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 need to continue physiotherapy as instructed.
- 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.
- 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
- 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.