Most hip and knee replacements are still in place decades later. None is guaranteed.

Registries report survival at 10, 20, and 25 years

A 2019 analysis of hip replacements pooled national registry data from Australia and Finland covering 215,676 operations. It found that 57.9 percent of hip replacements were still in place at 25 years ¹. The authors put it plainly: patients and surgeons can expect a hip replacement to last 25 years in around 58 percent of patients ¹.

The companion analysis for knees pooled 299,291 total knee replacements from 14 registries. It found 82.3 percent still in place at 25 years ². For partial (unicompartmental) knee replacements the figure was 69.8 percent ².

A UK population study of more than 117,000 hip and knee replacements reported the nearer milestones. Hip replacements had a 10-year survival of 95.6 percent and a 20-year survival of 85.0 percent ³. Knee replacements had 96.1 percent at 10 years and 89.7 percent at 20 years ³. The American Academy of Orthopaedic Surgeons states that more than 90 percent of modern total knee replacements are still functioning well 15 years after surgery ⁴.

Studies disagree, and the reason matters

The hip analysis above also pooled 44 published case series, which are reports from individual surgeons or centres. Those series gave a 25-year survival of 77.6 percent, against 57.9 percent from the registries ¹. The authors judged the registry figure less likely to be biased, because registries capture every operation in a country rather than the ones a centre chose to publish ¹.

So two honest numbers exist for the same question. When a figure is quoted, it is worth asking where it came from.

Age at surgery, weight, activity, and implant type all affect longevity

Age at surgery is measured directly in the registries. In the UK study, people who had a hip or knee replaced after age 70 had a lifetime risk of revision of about 5 percent ³. For men in their early 50s the lifetime risk of knee revision was 35 percent, and women of the same age had a lower risk than men ³.

Over a period of years the implant may wear or loosen, most often through everyday activity, and excessive activity or being overweight may speed that wear ⁵. A meta-analysis of 20 studies of knee replacement found that obese patients had higher odds of revision for any reason, with an odds ratio of 1.30, and higher odds of deep infection, with an odds ratio of 2.38 ⁶.

Implant type shows up in the registries too. In the pooled knee data, total knee replacements outlasted partial knee replacements at 25 years, 82.3 percent against 69.8 percent ². That is a population comparison; a partial replacement is chosen for reasons a survival figure does not capture.

• The AAOS lists unlimited walking, swimming, golf, driving, light hiking, biking, and ballroom dancing as realistic activities after knee replacement ⁴.
• Surgeons generally advise against high-impact activities such as running, jogging, and jumping ⁴.

Revision means a second operation to replace part or all of the implant

An implant can loosen from the bone over time, the plastic bearing can wear, and an infected joint may become stiff and painful as the implant loses its attachment ⁷. Instability, stiffness from scar tissue, and a fracture around the implant are the other common reasons a knee replacement is revised ⁷. For hips the list is similar: wear and loosening, infection, repeated dislocation, and fracture around the components ⁸.

Revision is a different operation from the first one. For knees it is longer and more complex, requires extensive planning, and needs specialised implants and tools ⁷. For hips it is likewise a more complex procedure that takes longer to perform than the primary replacement ⁸.

A person young enough to outlive an implant is choosing, in effect, the likelihood of a second and harder operation later in life ⁸.

No implant is guaranteed

The registry authors state the premise directly: given enough time, all hip and knee replacements would eventually fail ¹². The survival figures describe populations, and they are averages across implant designs, surgeons, and patients.

What the evidence supports saying is this. Most knee replacements and more than half of hip replacements are still in place at 25 years in national data ¹². Age at surgery, weight, activity, and implant type shift the odds, and a revision, if one is needed, is a larger operation than the first ³⁵⁶⁷⁸.

What to ask your surgeon

• Which registry or published survival figures does the implant you plan to use have?
• Given my age, what is the likelihood I will need a revision in my lifetime?
• Is there anything about my weight, activity, or health you would want changed before surgery?
• What activities would you expect me to return to, and which would you advise against?
• How will you follow the implant over the years, and what symptoms should bring me back early?

Your surgeon decides from your exam, imaging, and history. Survival figures describe populations, not any one joint.