Partial knee replacement preserves more of your natural knee than a total knee replacement, but it is not simply a smaller version of the same operation. It treats arthritis confined primarily to one compartment of your knee.

The procedure can provide excellent results for appropriately selected patients. It also carries trade-offs, including a higher revision rate than total knee replacement in large registry studies.

What a partial knee replacement replaces

Your knee has three compartments. The medial compartment is on the inside, the lateral compartment is on the outside, and the patellofemoral compartment is where your kneecap meets your thigh bone.

A partial knee replacement, also called unicompartmental knee arthroplasty, replaces the damaged surfaces in one compartment. The remaining bone, cartilage, and ligaments are preserved when they are sufficiently healthy and stable.

Partial knee replacement describes how much of your joint is replaced, not simply the size of your incision.

Many partial replacements use a smaller incision, which is why they are sometimes confused with minimally invasive surgery. A total knee replacement can also use a smaller-incision approach. The two terms describe different aspects of surgery.

Who may be a candidate

Candidacy depends on the location and pattern of arthritis, ligament function, alignment, motion, symptoms, and your surgeon’s assessment. Arthritis generally needs to be isolated to one compartment or clearly dominated by one compartment in a way that makes preservation reasonable.

Pain severity alone cannot determine eligibility. A person can have substantial pain but arthritis in several compartments. Another person may have less severe pain while imaging and examination show disease that is more suitable for a partial replacement.

Older rules sometimes excluded people based largely on age, weight, or activity level. Current selection is more individualized, but partial replacement is still not appropriate for everyone.

Why a partial knee may feel more natural

A partial replacement preserves more of your natural joint and often retains important ligaments, including the anterior cruciate ligament when it is functional. This can preserve aspects of your knee’s normal movement and sensation.

Some people report that a partial replacement feels more natural, particularly during the early months. Studies have also found shorter hospital stays and fewer early medical complications in selected partial-replacement populations compared with total replacement.¹

These potential advantages do not establish that partial replacement is the better operation for every eligible person. They need to be considered alongside implant longevity, arthritis progression, and surgeon experience.

The revision-rate trade-off

National joint registries consistently report higher revision rates for partial knee replacement than for total knee replacement. A large matched analysis of registry data found fewer short-term medical complications after partial replacement but a substantially higher risk of revision.¹

A revision is another operation performed to replace or modify an implant. After partial replacement, revision may occur because arthritis progresses in another compartment, the implant loosens, a mobile bearing dislocates, pain persists, or another mechanical concern develops.

Revision statistics require context. Research suggests that surgeons may have a lower threshold for revising a painful partial replacement because converting it to a total replacement can be less complex than revising an existing total replacement.² Even with that difference in clinical thresholds, the higher revision rate remains an important part of informed consent.

Surgeon experience is especially important

Partial knee replacement requires accurate patient selection, implant positioning, ligament balance, and surgical execution. Registry research has found that surgeons who perform partial replacements more frequently tend to have lower revision rates than surgeons who perform them occasionally.³

Ask your surgeon how often they perform partial knee replacements, how they determine candidacy, and what results they see in their own practice. Volume does not guarantee an individual result, but it provides useful context.

As an Amazon Associate I earn from qualifying purchases. This planner is included in an Amazon Creator Connections campaign, which may provide an additional commission at no added cost to you.

The Planners With Purpose B5 Medical Visit Logbook provides space to organize questions, medications, providers, appointments, symptoms, and notes from surgical consultations. The larger B5 format is useful when you want room to compare partial and total replacement recommendations in detail.

Questions to ask your surgeon

Ask which compartments contain arthritis and whether your ligaments and alignment support a partial replacement. Find out what makes you a stronger or weaker candidate and what alternatives your surgeon considers reasonable.

Ask about the surgeon’s annual partial-replacement volume, expected precautions, typical rehabilitation plan, and the reasons their patients most commonly require revision. Also ask what a future conversion to total replacement might involve if arthritis progresses.

You do not need to select the operation based on the smallest incision or quickest advertised timeline. The decision should account for your anatomy, symptoms, goals, long-term priorities, and the surgeon’s experience.

Rehabilitation is still necessary

Partial replacement may allow an easier early experience for some people, but strength, walking, balance, swelling, and knee motion still require attention. Your physical therapy plan should reflect your actual function rather than assumptions based on the surgical label.

The Knee Replacement Game Plan is my comprehensive prehab book for people who want to assess their starting point and prepare deliberately. It covers functional testing, prehabilitation, home readiness, medical considerations, and final pre-surgery planning. The book is almost finished, and you can sign up on the page to be notified when it becomes available.

For continuing practical education, be a Total Knee Success Insider. You will receive new episodes and resources relevant to your stage of the knee replacement process.

Partial and total replacement solve different problems

A partial replacement is not a shortcut, and a total replacement is not evidence that you waited too long. Each procedure addresses a different pattern of joint disease.

The strongest decision combines accurate diagnosis, appropriate selection, realistic expectations, and a surgeon experienced with the recommended procedure.

Episode 34 examines robotic-assisted total knee replacement, including what the technology does, what current research shows, and what robotics does not change.

Join the free Total Knee Success Insider for practical knee replacement education, new podcast episodes, and helpful resources. You can also sign up using the form at the bottom of this page.

This article provides general educational information. It does not determine candidacy, recommend a surgical procedure, replace a surgical consultation, or establish a physical therapist-patient relationship. A qualified orthopedic surgeon must evaluate your arthritis pattern, ligaments, alignment, health, and individual circumstances.

References

1. Liddle AD, Judge A, Pandit H, Murray DW. Adverse outcomes after total and unicompartmental knee replacement in 101,330 matched patients: a study of data from the National Joint Registry for England and Wales. Lancet. 2014;384(9952):1437-1445. doi:10.1016/S0140-6736(14)60419-0
2. Tay ML, Monk AP, Frampton CM, Hooper GJ, Young SW. A comparison of clinical thresholds for revision following total and unicompartmental knee arthroplasty. Bone Joint J. 2023;105-B(3):269-276. doi:10.1302/0301-620X.105B3.BJJ-2022-0872.R2
3. Liddle AD, Pandit H, Judge A, Murray DW. Effect of surgical caseload on revision rate following total and unicompartmental knee replacement. J Bone Joint Surg Am. 2016;98(1):1-8. doi:10.2106/JBJS.N.00487
4. Beard DJ, Davies LJ, Cook JA, et al. Total versus partial knee replacement in patients with medial compartment knee osteoarthritis: the TOPKAT randomized controlled trial. Lancet. 2019;394(10200):746-756. doi:10.1016/S0140-6736(19)31281-4
5. Hunt LP, Ben-Shlomo Y, Clark EM, et al. Patients receiving a primary unicompartmental knee replacement have a higher risk of revision than expected from their preoperative characteristics. Bone Joint J. 2021;103-B(4):696-704.
6. Sidhu A, Obana KK, Ray GS, et al. International primary knee arthroplasty registry review. J Arthroplasty. 2023;38(7):1229-1236.