Partial Versus Total Knee Replacement: What is the Differnce?

If you've been told you need a knee replacement, you may be wondering whether you need to replace the whole joint or whether a smaller, more targeted approach is possible. For a growing number of patients, partial knee replacement is a highly effective option that most people don't even know they might qualify for.

Here's what you need to know about partial knee replacement, how it compares to a total knee replacement, and whether it might be the right choice for your situation.

What Is a Partial Knee Replacement?

Your knee is made up of three distinct sections, called compartments. The medial compartment sits on the inner side of the knee. The lateral compartment is on the outer side. The patellofemoral compartment is where your kneecap connects to the thighbone at the front of the joint.

Osteoarthritis doesn't always damage all three compartments equally. In many patients, cartilage breakdown is limited to just one area of the knee while the rest of the joint remains in good shape.

Partial knee replacement, also called unicompartmental knee arthroplasty or a "uni," targets only the damaged compartment. The surgeon removes the worn cartilage and bone in that specific area and replaces it with an implant sized for your anatomy. Everything else stays intact, including the healthy cartilage in the other compartments and, critically, your ACL ligament.

A total knee replacement, by contrast, resurfaces all three compartments regardless of how much damage is present in each.

How Does Partial Knee Replacement Differ from Total Knee Replacement?

The differences between partial and total knee replacement go well beyond the size of the implant. They affect how the surgery is performed, how your knee feels afterward, and how quickly you recover.

The Incision and Surgical Approach

Partial knee replacement is performed through a much smaller incision than a total knee replacement. Because surgeons only need access to one section of the knee, there's significantly less disruption to surrounding muscle and soft tissue. The ACL and other key ligaments remain untouched.

Total knee replacement requires a larger incision and more extensive reshaping of the joint. The ACL is removed as part of the procedure, and the entire surface of the joint is resurfaced with implant components.

How the Knee Feels After Surgery

One of the most consistent findings in orthopedic research is that patients with partial knee replacements describe their knee as feeling more natural. When patients who have had a partial replacement on one knee and a total replacement on the other are asked which one feels better, they consistently prefer the partial knee side.

This makes sense anatomically. When only one compartment is replaced and the ACL is preserved, the knee retains much of its original structure and movement pattern. The joint still bends and responds the way your body expects it to.

With a total knee replacement, approximately 20% of patients report that they're never fully satisfied with how the knee feels, even when the procedure is technically successful.

Recovery Time

Recovery from partial knee replacement is considerably faster than recovery from total knee replacement.

About 90% of partial knee replacement patients feel recovered within three to four weeks. Most are back to daily activities within that same window, and many return to sports like golf, tennis, or cycling within six to ten weeks.

Total knee replacement typically requires two to three months before most patients feel fully recovered. Both surgeries take roughly the same amount of time in the operating room, around two hours, but the partial approach causes far less tissue disruption, which directly translates to a shorter recovery.

Many partial knee replacement patients go home the same day as surgery and are walking with minimal assistance within 24 hours.

Complication Rates

Because partial knee replacement is a less invasive procedure, it generally carries a lower risk of complications than total knee replacement. Blood loss is minimal. Risks such as infection, blood clots, and nerve injury exist with any joint replacement surgery but tend to occur less frequently with the partial approach.

Who Is a Candidate for Partial Knee Replacement?

Historically, only about 5 to 10% of knee replacement patients were considered candidates for a partial procedure. The surgery was technically demanding, and older instruments made precision difficult.

Advances in robotic-assisted surgical technology have changed that picture significantly. Studies now suggest that between 10% and 25% of patients who need knee replacement surgery may be eligible for the partial approach.

To qualify for a partial knee replacement, a patient generally needs to meet several criteria:

• Arthritis must be confined to one compartment of the knee
• The ACL and other major knee ligaments must be intact
• The knee must have a reasonable range of motion without severe stiffness
• There should not be a significant angular deformity such as severe bow-leggedness
• BMI should generally be below 40

Patients with rheumatoid arthritis typically don't qualify because inflammatory arthritis tends to affect the entire joint rather than a single compartment. Severe, multi-compartment osteoarthritis also makes total knee replacement the more appropriate choice.

Age is not a limiting factor in either direction. Younger, active patients often benefit most from partial knee replacement because the procedure places fewer restrictions on activity and allows for a more natural-feeling knee during high-demand activities like hiking or sport. Older patients who want a faster recovery and lower surgical risk can also be excellent candidates.

The Role of Robotic Assistance in Partial Knee Replacement

Partial knee replacement is widely recognized as technically more demanding than total knee replacement. The precision required is exceptional. If the implant is positioned even a few degrees off, the results can be problematic. Long-term implant loosening and accelerated wear in adjacent compartments are both possible consequences of imprecise placement.

This is exactly where robotic-assisted surgery has made the most meaningful difference.

With robotic assistance, the surgeon uses preoperative imaging to create a three-dimensional model of the patient's knee before the procedure ever begins. A personalized surgical plan is developed based on that patient's unique anatomy. During surgery, the robotic system provides real-time feedback and physical guardrails that keep bone removal within the planned boundaries with sub-millimeter accuracy.

The result is implant placement that matches each patient's anatomy with a level of consistency that manual techniques cannot reliably achieve. For partial knee replacement specifically, robotic assistance has moved this procedure from one that required exceptional surgical skill to produce consistent results, to one that can be performed predictably for appropriately selected patients.

As a joint replacement specialist serving patients throughout Middle Tennessee, Dr. Calendine uses robotic-assisted technology to perform partial knee replacement with a level of precision that directly supports better outcomes and longer implant longevity.

How Long Does a Partial Knee Replacement Last?

Longevity is one of the most common questions patients ask about partial knee replacement. The short answer is that a well-performed partial knee replacement in a well-selected patient can last as long as a total knee replacement, particularly in the first ten years after surgery.

Research shows that more than 90% of partial knee replacements are still functioning well at the ten-year mark. Some studies suggest the revision rate may be slightly higher for partial replacements over the second decade, but ongoing advances in surgical technique and robotic precision are continuing to improve those long-term numbers.

One practical advantage of partial knee replacement is that if revision surgery is ever needed, converting a partial replacement to a total knee replacement is generally straightforward. The anatomy is well preserved, and results from that kind of revision tend to be excellent. Revising a failed total knee replacement is a significantly more complex undertaking.

Many surgeons, including Dr. Calendine, no longer view partial knee replacement as a temporary or preliminary procedure. For the right patient, it should be their first and only knee surgery.

Is Partial Knee Replacement Right for You?

The best way to find out whether you're a candidate for partial knee replacement is a thorough evaluation with an orthopedic surgeon who has experience performing both partial and total knee replacement. Proper patient selection is the single most important factor in determining outcomes for partial knee replacement.

Your surgeon will review your X-rays and possibly an MRI, assess your knee's range of motion and stability, and discuss your activity level and functional goals. From there, a recommendation can be made based on your specific anatomy and needs.

If you're living with knee pain in the Nashville or Franklin, Tennessee area and want to understand your options, Dr. Cory Calendine and his team specialize in robotic-assisted knee replacement, including partial knee replacement, and can help determine whether this approach is appropriate for your situation.

This content is provided for educational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified orthopedic surgeon regarding your specific condition and treatment options. Individual results vary.