If knee arthritis has progressed to the point where replacement surgery is being considered, you may hear about two main options: total knee replacement and partial knee replacement.
The difference is straightforward in principle. A total knee replacement replaces the damaged surfaces across the main parts of the knee, while a partial knee replacement replaces only the compartment of the knee affected by arthritis.
But choosing between them is not simply a matter of deciding which operation is “better.” The right procedure depends largely on where the arthritis is located, how extensive the joint damage is, the condition of the ligaments and other parts of the knee, and your individual symptoms and goals.
If you want to understand knee replacement surgery more broadly, you can also explore our guide to Knee Replacement Surgery.
Total vs partial knee replacement at a glance
| Feature | Total Knee Replacement | Partial Knee Replacement |
|---|---|---|
| How much of the knee is replaced? | Damaged surfaces across the knee are replaced | Only the affected compartment is replaced |
| Typical use | Arthritis affecting multiple areas of the knee | Arthritis confined mainly to one compartment |
| Bone and tissue preserved | More of the damaged joint is replaced | More of the unaffected knee is preserved |
| Surgical extent | Generally more extensive | Generally less extensive |
| Recovery | Usually involves a longer overall recovery | Often allows faster early recovery in appropriately selected patients |
| Future arthritis | Less concern about arthritis developing in an unreplaced compartment | Remaining compartments can develop arthritis over time |
These are general differences. They do not mean that every person will experience the same recovery or long-term outcome.
What is total knee replacement?
In a total knee replacement, the surgeon removes and replaces the damaged joint surfaces of the knee with artificial components.
The procedure generally involves the lower end of the thighbone (femur) and the upper end of the shinbone (tibia). The underside of the kneecap may also be resurfaced depending on the patient's condition and the surgical plan.
Total replacement is commonly considered when arthritis has affected more than one area of the knee or when the overall pattern of joint damage makes a partial replacement unsuitable.
It does not mean that every structure in the knee is removed. The surgeon replaces the damaged joint surfaces while managing the surrounding ligaments and soft tissues according to the implant design and surgical technique.
What is partial knee replacement?
A partial knee replacement, also called a unicompartmental knee replacement, replaces only the damaged compartment of the knee. The knee has three main compartments:
- Medial compartment: the inner side of the knee
- Lateral compartment: the outer side of the knee
- Patellofemoral compartment: the area between the kneecap and thighbone
When arthritis is confined mainly to one compartment and the remaining parts of the knee are healthy enough, partial replacement may be an option for selected patients.
Why does the location of arthritis matter so much?
This is one of the most important differences between the two procedures. Imagine the knee as having several sections. If arthritis is limited to one section while the other compartments remain relatively healthy, replacing the entire knee may not always be necessary.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
However, if arthritis affects multiple compartments, a partial replacement cannot address all the damaged areas. In that situation, total knee replacement may be more appropriate because it treats the broader pattern of joint damage.
Who may be suitable for partial knee replacement?
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
Partial knee replacement is generally considered when the arthritis is isolated to one compartment and the rest of the knee is suitable for preservation. Doctors may consider factors such as:
- Arthritis being limited mainly to one compartment
- Reasonably preserved cartilage in the other compartments
- A suitable knee alignment
- A stable and functional ligament structure
- A knee that retains an appropriate range of movement
- Symptoms that are consistent with the affected compartment
- Overall health and ability to undergo and recover from surgery
These criteria are not simply a checklist that automatically qualifies someone for partial replacement. The surgeon needs to assess the entire knee.
Who is more likely to need total knee replacement?
Total knee replacement is more likely to be considered when arthritis affects multiple compartments or when the overall condition of the knee makes partial replacement unsuitable. This may include patients with:
- Arthritis affecting both the medial and lateral compartments
- More widespread joint damage
- Significant damage involving several parts of the knee
- Instability or ligament problems that make partial replacement unsuitable
- Severe deformity or alignment problems
- Other structural changes that cannot be adequately treated by replacing only one compartment
Is partial knee replacement less invasive?
Generally, yes. Because a partial knee replacement addresses only the damaged compartment, it preserves more of the patient's original knee and usually involves less extensive bone preparation than total knee replacement.
This can contribute to a faster early recovery in appropriately selected patients. However, “less invasive” does not automatically mean “better.” A partial replacement is only useful when the remaining knee is healthy and stable enough for the procedure to provide a durable result.
Which has a faster recovery?
Partial knee replacement often allows a faster early recovery than total knee replacement in appropriately selected patients. Patients may experience less postoperative pain, regain movement sooner and return to everyday activities more quickly.
However, recovery varies considerably between individuals. A patient's age, general health, physical condition before surgery and rehabilitation all influence the outcome.
It is therefore better to think of partial replacement as having the potential for a quicker recovery rather than assuming that every patient will recover faster.
Which gives a more natural-feeling knee?
One potential advantage of partial knee replacement is that more of the patient's natural knee is preserved. Because the procedure replaces only one compartment, the remaining parts of the knee and some of its natural structures continue to function.
Some patients therefore report a more natural feeling or movement after partial knee replacement. However, this does not mean that every patient will notice a major difference. The final experience depends on the condition of the knee, implant positioning, rehabilitation and individual perception.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
Which surgery has fewer complications?
Partial knee replacement can have advantages related to its smaller surgical scope, including potentially faster recovery and lower rates of some early complications in appropriately selected patients.
However, partial replacement also has an important consideration: the parts of the knee that are not replaced remain vulnerable to future arthritis.
If arthritis later develops or progresses in another compartment, additional surgery may become necessary. Therefore, comparing complication rates alone does not provide the complete picture. Doctors also consider the likelihood of long-term success and the possibility of revision surgery.
Which lasts longer: total or partial knee replacement?
This question does not have a simple universal answer. Both total and partial knee replacements can provide durable improvement, but partial replacement has a particular long-term consideration: the remaining natural compartments can develop arthritis over time.
If that happens and symptoms become significant, a revision procedure may eventually be needed. Total knee replacement replaces the major damaged joint surfaces at the time of the original surgery, so there is less concern about arthritis developing in an unreplaced tibiofemoral compartment.
However, total replacement can also require revision for reasons such as implant wear, loosening, infection or other complications. The long-term result therefore depends on the individual patient, implant, surgical technique and progression of disease.
Does age determine whether you should have total or partial replacement?
Age alone should not determine the choice. A younger patient is not automatically a better candidate for partial replacement, and an older patient is not automatically better suited to total replacement.
The condition of the knee is much more important. The surgeon considers the location and extent of arthritis, ligament function, alignment, range of movement, overall health and the patient's goals.
What are the main advantages of total knee replacement?
Total knee replacement can be advantageous when the disease is widespread because it addresses the major damaged surfaces in one operation. Potential advantages include:
- Treating arthritis across multiple compartments
- Reducing pain caused by widespread joint damage
- Improving knee function and mobility
- Avoiding the problem of leaving severely arthritic compartments untreated
- Providing a well-established treatment for advanced, widespread knee osteoarthritis
What are the main advantages of partial knee replacement?
When a patient is appropriately selected, partial replacement can preserve more of the natural knee while treating the damaged compartment. Potential advantages include:
- Preservation of unaffected parts of the knee
- Less extensive bone removal
- Potentially faster early recovery
- Potentially less postoperative pain
- A more natural-feeling knee for some patients
- Smaller surgical intervention in appropriately selected cases
So which is better: total or partial knee replacement?
Neither is universally better. If arthritis is confined to one compartment and the rest of the knee is suitable, partial replacement may offer important advantages. If arthritis affects multiple compartments or the knee has other structural problems, total replacement may be the more appropriate option.
The best procedure is therefore the one that matches the patient's actual pattern of disease. For people with isolated medial compartment osteoarthritis who are suitable for both procedures, current NICE guidance recommends discussing the risks and benefits of both options and involving the patient in the choice.
The Bottom Line
Total and partial knee replacement are not competing procedures where one is automatically better than the other. They are designed for different patterns of knee disease.
Partial knee replacement may be a valuable option when arthritis is confined mainly to one compartment and the remaining knee is healthy and stable enough to preserve. It can offer a less extensive operation and potentially faster early recovery while retaining more of the natural knee.
Total knee replacement is generally more appropriate when arthritis affects multiple compartments or when other structural problems make partial replacement unsuitable. It addresses a broader area of joint damage in one operation.
The decision should therefore be based on where the arthritis is, how extensive the damage is, how stable and mobile the knee remains, and what treatment is most likely to provide durable improvement.
For patients who are suitable for either procedure, discussing the benefits, risks, recovery and possibility of future surgery with the orthopaedic team allows the choice to be made around the individual's circumstances and preferences.
