Evidence guide

Partial vs total knee replacement

If arthritis affects only one part of your knee, a partial knee replacement may be an option. Here is how the two compare.

Last reviewed October 8, 2026

The short answer

What's the difference?

The knee has three compartments: inner (medial), outer (lateral) and behind the kneecap. A total knee replacement resurfaces all of them. A partial (unicompartmental) knee replacement resurfaces only the worn one, most often the inner side, and keeps the healthy cartilage and ligaments.

Not everyone qualifies. A partial knee is generally an option only when the arthritis is confined to one compartment and the ligaments are intact. Your surgeon decides based on your X-rays and exam.

How they compare

OutcomePartialTotal
Function at 5 years (TOPKAT)No significant difference in Oxford Knee Score1
Cost-effectiveness (TOPKAT)More quality-adjusted life-years, lower cost1Reference
Hospital stayAbout 1 to 2 days shorter2Reference
Annual revision rateAbout 1.1%3About 0.5%3
Still in place at 25 yearsAbout 70%4About 82%4

Reading the revision numbers carefully

Revision is only one outcome. The same review that found higher revision rates for partial knees also found lower mortality, fewer blood clots and fewer heart problems after partial knee replacement in registry data.2 The TOPKAT authors concluded that partial knee replacement should be considered the first choice for suitable patients with isolated inner-knee arthritis.1

Questions to ask your surgeon

  1. Is my arthritis limited to one part of the knee?
  2. Am I a candidate for a partial knee replacement? Why or why not?
  3. How many partial knee replacements do you do?
  4. If I later need a total knee, what would that involve?

Sources

  1. Beard DJ, et al. The clinical and cost-effectiveness of total versus partial knee replacement in patients with medial compartment osteoarthritis (TOPKAT): 5-year outcomes of a randomised controlled trial. Lancet. 2019;394(10200):746-756. doi:10.1016/S0140-6736(19)31281-4
  2. Wilson HA, et al. Patient relevant outcomes of unicompartmental versus total knee replacement: systematic review and meta-analysis. BMJ. 2019;364:l352. doi:10.1136/bmj.l352
  3. Chawla H, et al. Annual revision rates of partial versus total knee arthroplasty: a comparative meta-analysis. Knee. 2017;24(2):179-190. doi:10.1016/j.knee.2016.11.006
  4. Evans JT, et al. How long does a knee replacement last? A systematic review and meta-analysis of case series and national registry reports with more than 15 years of follow-up. Lancet. 2019;393(10172):655-663. doi:10.1016/S0140-6736(18)32531-5

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