Thirteen years in the middle.

Most people with a bad knee hear the same advice. Do the exercises, lose a little weight, and when that stops working, consider surgery. One US simulation estimated that once non-surgical treatment stops working, people wait on average about 13 years for a knee replacement, though for some it is far shorter or longer.¹ Those years are spent with a hand on the stair rail, choosing chairs by their height, and quietly giving up the parts of the house that ask most of a knee.

What it does to a day

Knee osteoarthritis rarely arrives as an event. The pain comes and goes, and then it stays. In any one year, about a quarter of people over 55 have a persistent episode of knee pain. About one in ten has painful, disabling knee osteoarthritis, and a quarter of those are severely disabled. In the UK and the Netherlands, only about one in six people with persistent knee pain sees a doctor about it that year.²

For families, that last number matters. Most of this happens out of sight. The pain is usually worst with repeated bending and on stairs.³

How many people

About 595 million people worldwide had osteoarthritis in 2020,⁴ and the knee is the joint it affects most often.⁵ The number of knee cases is projected to rise by about 75 percent by 2050, as populations grow and age and as obesity becomes more common.⁴ In one long-running study in North Carolina, the lifetime risk of developing painful knee osteoarthritis by age 85 was about 45 percent, nearly one in two, and about two in three for people with obesity.⁶

It is expensive to live with, too. In US insurance claims, people with knee osteoarthritis had $7,707 more in total health care costs a year than people of the same age, sex and insurance type without it.⁷

What helps, and its limits

The American College of Rheumatology's guideline puts exercise and, for people who are overweight, weight loss at the centre of treatment. It also strongly recommends self-management programmes, tai chi and, for some people, a cane or a knee brace.⁸

Weight matters for a mechanical reason. In a study of overweight and obese older adults with knee osteoarthritis, each pound lost was associated with about four pounds less load on the knee with every step.⁹

Exercise helps, but less than its reputation suggests. The 2024 Cochrane review of 139 trials found that exercise improves knee pain by about 9 to 13 points and function by about 10 to 13 points on a 100-point scale. On average those short-term gains sit close to the smallest change patients typically notice, so the authors call them of "uncertain clinical importance".¹⁰ It is still a first-line, strongly recommended treatment.⁸ But it is not enough for everyone, and the benefits fade when people stop.³

Surgery, and who it leaves out

When the pain becomes too much, the usual answer is a total knee replacement. The same US model estimated that about 54 percent of people with knee osteoarthritis will eventually have one.¹ In 2014 there were about 681,000 primary knee replacements in the United States. One projection, which assumes current trends continue, puts the number at about 1.9 million a year by 2030 and 3.4 million by 2040.¹¹

US knee replacements could rise fivefold

Primary total knee replacements per year. 2014 is actual; later years are projections that assume current trends continue.

2014, actual681,000

2030, projected1.92 million

2040, projected3.42 million

Source: Singh et al., Journal of Rheumatology (2019). The 2040 projection has a wide range, from 2.5 to 4.7 million.

Europe is on the same path. Surgeons in the EU performed about 791,000 knee replacements in 2023, and the rate rose over the previous decade in 23 of the 24 countries with data.¹²

Surgery helps many people a great deal. It does not help everyone. In a large Canadian study, about one in five people who had a primary knee replacement were not satisfied with the result,¹³ and in the best long-term studies about 20 percent still report an unfavourable level of pain afterwards.¹⁴

The people in the middle

That leaves a large group: people who are not ready for surgery, or not candidates for it, or who have had it and still struggle. They do the exercises. They still find the stairs hard. They are the people we think about most when we design.

We built Veema's first design around the hip and the knee together because standing up and climbing stairs ask the most of a knee. (We explain why in Why standing up gets so hard.) Whether an exoskeleton can help people living with knee osteoarthritis is a question only studies with older adults can answer.

These figures describe the need. They are not results or claims about Veema.

Sources

1. Losina et al., Arthritis Care and Research (2015): US simulation model (OA Policy Model): 54% of people with knee osteoarthritis undergo total knee replacement in their lifetime; about 13 (SD 10) years waiting for surgery after non-surgical treatment fails.
2. Peat, McCarney and Croft, Annals of the Rheumatic Diseases (2001): review: about 25% of people over 55 have a persistent episode of knee pain in a year; about 10% painful disabling knee osteoarthritis, a quarter of them severely disabled; in the UK and the Netherlands about one in six consult a GP in that year.
3. Hsu and Siwiec, Knee Osteoarthritis, StatPearls (2023): symptoms typically worse with repetitive bending or stairs; exercise benefits are lost after about 6 months if exercises are stopped.
4. GBD 2021 Osteoarthritis Collaborators, Lancet Rheumatology (2023): 595 million people with osteoarthritis in 2020; knee osteoarthritis cases projected to rise 74.9% between 2020 and 2050, driven by population growth, ageing and obesity.
5. World Health Organization, Osteoarthritis fact sheet: knee is the most frequently affected joint, with a prevalence of 365 million (2019).
6. Murphy et al., Arthritis and Rheumatism (2008): Johnston County, North Carolina cohort: lifetime risk of symptomatic knee osteoarthritis by age 85 of 44.7%; about 2 in 3 among people with obesity.
7. Bedenbaugh et al., ClinicoEconomics and Outcomes Research (2021): US claims 2011 to 2017: patients with knee osteoarthritis had $7,707 more total health care costs per year than controls matched on age, sex, payer and region.
8. Kolasinski et al., 2019 ACR/Arthritis Foundation Guideline, Arthritis Care and Research (2020): strong recommendations for exercise, weight loss for people who are overweight, self-management programmes, tai chi, cane use and, for knee osteoarthritis, tibiofemoral knee braces.
9. Messier et al., Arthritis and Rheumatism (2005): overweight and obese older adults with knee osteoarthritis: each pound of weight lost associated with a fourfold reduction in knee load per step.
10. Lawford et al., Exercise for osteoarthritis of the knee, Cochrane Review (2024): 139 trials, 12,468 participants; pain improved 8.7 to 13.1 and function 9.7 to 12.5 points on 0 to 100 scales across comparisons; benefits of uncertain clinical importance; low to moderate certainty, short-term.
11. Singh et al., Journal of Rheumatology (2019): 680,886 primary total knee replacements in the US in 2014; projected 1.92 million in 2030 and 3.42 million in 2040 (prediction interval 2.46 to 4.75 million) if current trends continue.
12. Eurostat, Surgical operations and procedures statistics: 791,000 total knee replacements in the EU in 2023, 176.4 per 100,000 inhabitants; rates rose in 23 of 24 countries with data, 2013 to 2023.
13. Bourne et al., Clinical Orthopaedics and Related Research (2010): 1,703 primary knee replacements in Ontario, Canada: about one in five (19%) patients not satisfied.
14. Beswick et al., BMJ Open (2012): 10% to 34% of patients report an unfavourable long-term pain outcome after knee replacement; about 20% in the highest-quality studies.