Partial knee replacement
What is involved?
Your knee joint is made up of three 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 occasion, one or two 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.
The 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 ones, to create a smooth articulation of the joint.
The replacement parts are held in place either with a specialised bone cement or with implants, coated in a substance that allows the bone to grow on to 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 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 situation, 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 over total knee replacement are: normally a faster rehabilitation and preservation of the non-affected parts of your knee, including the cruciate ligaments. Generally, partial knee replacements feel more natural than total knee replacements, and will often mean you can get back to a higher level of activity than if you have had 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.
We are committed to ensuring our patients have the most up-to-date and efficient post-operative rehabilitation. We use Hilotherm cold water therapy; when you are transferred back to the ward, your knee will be wrapped in a specialised cooling device which provides compression and the circulation of 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, as early mobilisation, with the assistance of crutches or sticks, has been shown to reduce pain, lower the risks of blood clots, and improve the long-term outcome following knee surgery. The leg may be swollen and bruised, so, to reduce this, continued ice therapy and elevation is useful in the days following surgery.
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 one to three nights, depending on your comorbidities (any other medical conditions) and your personal preferences. Following discharge, your surgeon will arrange to see you at between two to three weeks after surgery to check your wound and ensure you are progressing as planned.
Recovery milestones
Days 1 to 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.
Weeks 1 to 2: Over this period of time the swelling and bruising in your knee will gradually subside. 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 an 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 the best result.
Week 2 to 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.
Months 3 to 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. It is not unusual for there to be good days and bad days, and this is perfectly normal.
Frequently asked questions
How is the wound closed?
You will have a straight wound over the front of your knee between 15cm and 30cm long. This can be closed with either metal clips or dissolving stitches. Please ask your 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 again. Recent research has indicated that on average this is between four to six weeks after surgery. 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, you would hope to return to work after approximately six weeks. But if your job involves manual work, it may be more like three to four 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 per cent of patients, however, find it too uncomfortable to kneel, and this is normally related to the level of discomfort in kneeling prior to surgery.
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 that do not place too much strain on the knee joint, such as walking, cycling, golf, bowls, hiking and swimming. However, more active sports, such as football, squash and skiing, can be difficult after a partial knee replacement. Talk to your surgeon about your specific case, and 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 can set off airport security alarms, and it is advisable to take evidence of your surgery with you when travelling. On most occasions, if you show airport staff your scar, they will accept this as evidence.
How long does a partial knee replacement last?
Advances are being made in arthroplasty surgery all the time. We have much more sophisticated plastic bearing surfaces available now, compared to those that were used in the past. Wear of this plastic bearing was the most common reason for knee replacements requiring revision. 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 at least 15 to 25 years.
The advantage of a partial (over a total) knee replacement is that, if any part of it needs revising or if arthritis progresses, is a relatively straight forward procedure to go back in and do any necessary further work.
