Is it the right time for a knee replacement?

Knee replacement is the most common inpatient surgery in the U.S. That does not make the decision to have one easy - especially if you are younger than 60.

Older and younger people benefit equally from knee replacement, provided they are generally healthy to begin with. Even so, people under 60 are encouraged to postpone total knee replacement if they can.

Why? Artificial joints have a limited life span. At an average activity level, today's implants can be expected to last 15 to 20 years, sometimes longer. But if you are overweight or more active than average, the new joint faces extra stress and may wear out sooner.

Ideally, your first knee replacement is your last. Given the average American life span, most older adults who receive a new knee will never need it replaced.

The picture grows more complicated in your 40s or 50s, when a new knee is more likely to wear out within your lifetime. That means a revision surgery to remove the old implant and put in another. And the number of people under 55 having knee replacements is rising fast.

Waiting too long carries its own risks. If cartilage and bone breakdown leaves the joint crooked, surgery becomes more complicated - such deformities can make you bow-legged or knock-kneed. Some research also suggests people who wait until they have significant disability may benefit less in the long run, though other studies find no difference in results for those who delay.

When to have a knee replacement is a deeply individual decision - one more reason shared decision-making between you and your doctor matters so much.