What is it?
Your knee joint is made up of 3 compartments: the medial compartment, the lateral compartment, and the patellofemoral compartment (kneecap joint). Arthritis can affect the knee in a variety of patterns. It may involve the entire knee joint or on occasions 1 or 2 compartments in isolation. In this situation it may be appropriate to replace only the affected compartment or compartments rather than doing a total knee replacement. Options available include medial compartment replacement, lateral compartment replacement or patellofemoral joint replacement, sometimes in combination. The knee joint is opened in much the same way as a total knee replacement although normally a smaller incision is required. The worn out sections of the knee joint are then removed using special instruments and replaced with a combination of metal and highly specialised plastic to create a new smooth articulation within the portion of the knee joint that was previously worn out. These are held in place either with a specialised bone cement or with implants coated in a substance that allows the bone to grow onto them. There are many different types of partial knee replacement including mobile bearing, fixed bearing and customised implants and we would recommend you speak to your treating surgeon about the options that would best suit your knee.
Why would I need a partial knee replacement?
Partial knee replacements are suitable for people where a degenerative process has led to part of the knee joint becoming worn out causing pain and stiffness. In this setting replacing that section of the knee can restore movement and relieve pain allowing you to get back to a normal life. The benefits of partial knee replacement over total knee replacement are less perioperative morbidity, normally a faster rehabilitation, preservation of the non-affected parts of your knee including the cruciate ligaments. This means partial knee replacements feel more natural than a total knee replacement and in general will allow you to get back to a higher level of activity than a total knee replacement.
What happens after surgery?
The procedure is normally carried out under a spinal anaesthetic where your legs are numb. This can be combined with various levels of sedation to ensure you are either fully awake during the surgery or have no recollection of it. The spinal anaesthetic will also help with pain control immediately following surgery.
At One we are committed to ensuring our patients have the most up to date and efficient post-operative rehabilitation. When you are transferred back to the ward your knee will be wrapped in a specialised cooling device which provides compression and circulating cold water circumferentially around the knee to reduce pain and swelling. You will be offered pain killers and the nursing staff will take regular observations. Once you have fully recovered from the anaesthetic our expert physiotherapy team will get you up and walking on the day of surgery. You will be able to bear your full weight through the replaced knee immediately and early mobilisation with the assistance of crutches or sticks has been shown to reduce pain following knee replacements, lower the risks of blood clots and improve your long term outcome. The leg may be swollen and bruised so continued ice therapy and elevation is useful in the days following knee replacement surgery to reduce this. You will have an x-ray of your partial knee replacement on the day of surgery which will be checked by the surgical team prior to your discharge. The average length of stay following a partial knee replacement is between 1-3 nights depending on your medical comorbidities and your personal preferences. Following discharge your surgeon will arrange to see you at between 2-3 weeks post-operatively to check your wound and ensure your progressing as planned.
Days 1 – 4: Over this period of time you will take regular pain killers and have regular physiotherapy, once you are safe on your feet and would like to go home you will be discharged by the physiotherapy team.
0 – 2 weeks: Over this period of time the swelling and bruising will gradually subside in your knee. You must keep the dressing on at all times to maintain the sterile environment around the knee wound and allow it to heal. If the dressing becomes soaked through with blood and leaks our expert ward team will see you to re-dress it in appropriate fashion. Over this period rest, ice and elevation, as well as gently bending and straightening the knee, will ensure it settles down and you achieve best results.
Week 2 – 12: Over this period of time your range of movement will continue to improve, you may occasionally find the knee swells and becomes uncomfortable if you do a lot of walking but this is nothing to be worried about. Gradually your physiotherapists will work with you to improve the strength around your knee and you will find you’ll be able to walk longer distances over time.
Month 3 – 18: Recovery from a partial knee replacement is long and requires patience. Over a period of up to 18 months the soft tissues around your knee will settle and soften and your knee will feel more and more natural over this period of time. It is not unusual for there to be good days and bad days over this period and patience is definitely a virtue.
Frequently asked questions
- How long will I be in hospital?
The average stay is between 1 and 4 nights dependent on factors directly relating to your case. Please indicate to your surgeon the length of time you feel you would benefit in hospital and we can plan your recovery accordingly.
- How is the wound closed?
You will have a straight wound over the front of your knee between 15-30cms long. This can be closed with either metal clips or dissolving stitches. Please ask your treating surgeon what their preference is as it varies in each case.
- When can I start to drive again?
There will be no damage to your partial knee replacement if you start driving however, the DVLA state that it is the responsibility of the driver to ensure they are always in control of the vehicle. In reality when you feel you can press down hard enough to perform an emergency stop with the operated leg, this is a good indicator of when you could start driving. Recent research has indicated that on average this is between 4-6 weeks post-operatively. It is advisable to notify your insurer that you have had surgery and intend to start driving again.
- When can I return to work?
This depends on the type of work you do and whether or not you have a long commute. As a rough guide, if you have an office based job one would hope to return to work after approximately 6 weeks but if your job involves manual work it may be more like 3-4 months.
- Can I kneel after a partial knee replacement?
Yes. There are no restrictions to your ability to kneel after having had a partial knee replacement. Approximately 30% of patients however find it too uncomfortable to do so following knee replacement surgery and this is normally related to the level of discomfort in kneeling pre-operatively.
- When can I return to sports?
Return to sports is generally dependent on how quickly you recover following surgery and the complexity of your partial knee replacement operation. It is advisable not to return to sport until you have adequate flexibility, strength and fitness as it can lead to injury if you return too soon. It is realistic to expect to return to activities which do not place too much strain on the knee joint such as walking, cycling, golf, bowls, hiking and swimming however higher level activities such as football, squash and skiing can be difficult after a partial knee replacement and you will need to talk to your surgeon about your specific case as to whether or not it is advisable to return to these activities.
- Will my partial knee replacement set off airport metal detectors?
In most instances metal joint replacements are likely to set off airport security alarms and it is advisable to take evidence of your surgery with you when travelling however, on most occasions, if you show them your scar they will accept this as evidence.
- How long does a partial knee replacement last?
Advances are being made in arthroplasty surgery continuously. We currently have much more sophisticated plastic bearing surfaces available in comparison to those that were put in historically. Wear of this plastic bearing was the most common reason for knee replacements requiring revision. It is therefore likely that the knee replacements we are putting in today will last longer than those put in previously. As a rough estimate we would hope that your knee replacement would last 15-25 years at a minimum.
In the setting of partial knee replacement surgery, one of the benefits is that if the knee replacement wears out or if arthritis progresses in the other compartments of the knee revision of the partial knee replacement to a total knee replacement is a relatively straight forward procedure and can lead to outcomes similar to having a primary total knee replacement.