© 2019 OA Knee Pain. All Rights Reserved.

If your knee injury is contained within one compartment, you may be a candidate for a unicompartmental procedure, or partial knee replacement surgery. This option involves a direct replacement of the damaged bone with either metal or plastic components.

A knee joint comprises the ends of the femur, or thigh bone, and the tibia, the shin bone. These bones usually glide smoothly as they have smooth cartilage in between. Ligaments hold the joint in place and are shielded by the patella, or kneecap.

There are three compartments within the knee.

  • The medial compartment is the inside of the knee
  • The lateral compartment is the outside of the knee
  • The patellofemoral compartment refers to the front of your knee, between the kneecap and thighbone
Diagram of the human knee | OA Knee Pain Diagram of the human knee

A knee in full working order will glide smoothly because the ends of the bones, the knee joints, are covered by cartilage. As we age, all of the compartments in our knees can start to erode. This can cause painful conditions and injuries that affect our movement and quality of life, such as osteoarthritis.

If you develop osteoarthritis the cartilage is damaged and starts to wear away. Without the cartilage protecting the ends of the bones, they can become rough and this may cause the joint to stick (or where you may hear a grating sound). As a result your knee may be stiff, painful and you may find that your range of movement is reduced.

However, knee problems can start at any age due to wear and tear or injury. Partial knee replacement is preferred by younger patients as it allows for faster recovery and is usually much less painful than with complete knee replacement. Despite being a preferred option from a surgical perspective, many patients do try to avoid surgery in the first instance, instead opting for non-surgical options such as the use of a knee brace in conjunction with physio, medication and lifestyle changes.

Unicompartmental knee replacement

Before agreeing to this surgery your consultant will explain each stage of this treatment and recovery to you. You will be asked to sign a consent form to confirm that you understand what will happen during the procedure and that you also accept both the benefits and risks that may occur during the operation and as you recover.

This surgery is minimally invasive and can take place under general or spinal anaesthetic. It usually takes two hours to complete this operation. In order to make a full assessment and examine each compartment within the knee, the surgeon will make a small incision. This will enable them to confirm which part of the knee is damaged.

The damaged part will be removed and replaced by metal caps or covers. These will be held in place by cement, with a plastic insert placed between the two caps to allow for smooth movement.

Once the operation is over, you’ll be taken into recovery. If deemed necessary, a small tube may be placed in your wound to drain away any excess fluid.

Advantages of this method:

  • Unicompartmental knee replacement is beneficial in terms of a faster recovery, allowing a return to normal movement far quicker than with a full knee replacement.
  • You should experience good joint function and better knee function generally with partial knee replacement surgery.
  • This procedure involves minimal interference with the other knee compartments as a smaller incision is sufficient.
  • Bone removal is far smaller than with other methods to resolve knee problems.
  • There is less likelihood of any complications related to blood loss, meaning that there is no need to give blood before the operation.

Risks of unicompartmental knee replacement

  • If you experience problems in your joint at a later date, you are more likely to need joint revision surgery in the future, compared to those who opt for full knee replacement to begin with (though the lifespan of this surgery is up to around 15 years before a new knee replacement is required).
  • There are some risks with unicompartmental knee replacement surgery (as with any surgery) and one of the reasons why non-surgical solutions are sort out in the first instance.
  • You will not know if your knee has the healthy ligaments needed for the procedure until the time of the surgery when the incision and evaluation are made.
  • You will be more likely to require future intervention on your knee if you have undergone only a partial knee replacement.

What to expect during recovery

It is normal to feel sore and tender post-operation and this can be managed with pain medication. You might need to wear support stockings to assist with your circulation and you will also be assigned to a physiotherapist who will be able to help you with movement.

After two or three days, you will have an X-ray to check everything is in position and if everything is normal at this point, you will be discharged.

At home post-surgery

It’s critical to your recovery that you complete the exercises given to you by the physiotherapist once you return home. Also continue to take your pain management medication and inform your GP when you run out. Keep taking the medication until you are pain free. If you have been told to wear support stockings, continue to do so for at least 4-6 weeks.

If possible, ask someone to either stay with you or check in with you daily during your first few weeks at home. Your movement will be different than it was before the procedure and you may need assistance with some tasks as you may be using crutches or experiencing stiffness in your leg.

Your physiotherapist may, for example, recommend that you exercise for 20-30 minutes several times per day and/or walk for 30 minutes several times per day. Try to rest your knee as much as possible when you are not completing the exercises and gradually reintroduce your typical level of physical activity.

You should not drive until you have a follow up assessment with your consultant or GP and they agree that you are ready to do so. If you have stitches, these will be removed. It will be easier to use a shower than a bath while you are in recovery.

Partial Knee Replacement - OA Knee Pain It’s important you stick to the exercises given to you by the physiotherapist

Return to work

A timescale for returning to work will depend on the type of work you do, but should usually be possible within two to three months for most occupations. It will also depend on your rate of recovery.

As a general guide, if you have a desk job you could be ready to return after eight weeks. If you have a more physical job, you should be able to return around 12 weeks after the procedure if there are no further complications.

If you are able to, discuss a phased return to work with your employer and ask for any adjustments that will ease this process for you. If you are able to work from home for some or all of your duties, this will ease the pressure on your knee as it recovers.

Discuss adjustments that will support your return to work with both your GP and HR representative before you undergo the procedure. This will enable you and your employer to plan effectively and ensure that things run smoothly.

Adjustments might include the following, either in isolation or in combination:

Modifying your duties: If there are physical tasks that you will find difficult or impossible to complete whilst you are in recovery. These might include tasks where you need to lift and carry items or where you need to kneel or sit. They could also include mentally rigorous tasks that might require a level of concentration made difficult by any pain or pain management.

Reducing your hours of work: If possible, ask for reduced hours while you are in recovery to allow for the extra time it may take you to complete tasks at work and at home.

Modifying your working hours: If you have a busy commute, and home working isn’t available, you will need to avoid travelling during peak commuter times. If you use public transport, consider whether you can make your journey using different routes or methods, if these will be easier to manage while you are working your way back to full movement.

Relocation. If you work for a large company with multiple offices or outlets, could you work from a different, more convenient location? If you need to remain in your current location, is there another part of the building that would reduce the need to use stairs, allow you to access facilities more easily, or provide better space.

Transportation: If you usually drive yourself to work, it may be possible for a colleague who lives locally to drive you to and from work. Some companies will pay for taxis and most will allow a concession to permit you to use disabled parking spaces whilst you are in recovery.

Equipment: Most employers will be happy to provide any equipment that facilitates an easier return to the workplace and/or normal duties. This could include footstools, adjustable chairs and desks or alterations to existing equipment.

Frequent breaks: You should continue with your recommended exercises and activities once you are back in the office. Notify your manager and HR representative of what you are required to do, and ensure that your co-workers are also aware. Identify a space in which you can complete your exercises that will be available when you need it.

Long term prognosis

It is anticipated that most patients will make a full recovery after six to eight months. As with any procedure, it is possible that there will be resulting complications.

You should expect some level of pain, but it should not be overwhelming as this type of surgery is minimally invasive. Your need for pain management will depend on your tolerance and individual circumstances.

You should always seek advice from your GP if your pain continues beyond a reasonable amount of time, or if you experience bleeding, have difficulty passing urine or develop an infection on the wound site.

Sign up to the OA Knee Pain newsletter