The forecast in your knees.

The sky turns the colour of pewter, and somewhere around the kneecap a familiar ache arrives before the first drop of rain does. If you live with stiff joints, you probably know the feeling, or have heard it announced at breakfast: the knee says rain.

It is one of the oldest ideas in medicine. "Weather has been thought to affect symptoms in patients with arthritis since Hippocrates," said Will Dixon, then professor of digital epidemiology at the University of Manchester, in 2019. "Around three quarters of people living with arthritis believe their pain is affected by the weather," he added.¹

A European study puts a firm number on it. Among older adults with osteoarthritis in six countries, 67.2% said the weather affected their joint pain, and those people reported more pain on average than the rest: 4.1 against 3.1 on a 0 to 10 scale.² Women, people with anxiety and those living in southern Europe were more likely to call themselves weather sensitive.² So what happens when researchers check the forecast against the pain?

What the biggest studies found

In 2017 a team led by Anupam Jena took United States Medicare records for 1,552,842 people aged 65 and over, covering 11,673,392 visits to general internists between 2008 and 2012, and matched each visit to rainfall at local weather stations.³ If wet days sent knees and backs into revolt, more of those visits should have been for joint or back pain. They were not. After adjustment, 6.35% of visits on rainy days were for joint or back pain, against 6.39% on dry days, a difference that ran the opposite way to the belief and was far too small to matter clinically.³

Claims data have a blind spot: plenty of people with an aching knee never book an appointment; they simply have a worse day. So the European Project on OSteoArthritis asked the people themselves. It followed 810 adults aged 65 to 85 with knee, hand or hip osteoarthritis, who kept two-week pain calendars at three points over more than a year, and compared their entries with local weather records.⁴ Pain tracked daily humidity, and the link was stronger on colder days. But day-to-day changes in the weather, the shift people usually blame, were not significantly associated with pain at all.⁴

In Australia, Manuela Ferreira and colleagues tried a different design. Around 350 people with knee osteoarthritis took part, and the team compared the weather when each person first noticed a bout of pain with the weather one week and one month earlier, using Bureau of Meteorology records.⁵ Announcing the results alongside a similar study of back pain, the George Institute reported no link. "People who suffer from either of these conditions should not focus on the weather," Ferreira said.⁵

A fair hearing on a phone

The most generous test of the belief came from the United Kingdom. In 2016 Dixon's team recruited more than 13,000 people across 124 postcode areas, from Orkney to the Isles of Scilly, through a smartphone app called Cloudy with a Chance of Pain.¹ Analysing daily data from 2,658 of them, the researchers found "significant yet modest relationships between pain and relative humidity, pressure and wind speed," links that held even after accounting for mood and physical activity.⁶

Modest is the right word. In the university's summary, on damp, windy days with low pressure, the chance of more pain was around 20% higher than on an average day. If your chances of a painful day on an average day were 5 in 100, they would rise to 6 in 100.¹ Rainfall showed no association, nor did temperature on average.¹

When Ferreira's group later pooled the evidence, combining 11 case-crossover studies with 15,315 participants and 28,010 pain events, they found no association between humidity, air pressure, temperature or rainfall and pain in rheumatoid arthritis, knee pain or low back pain.⁷ The one exception was gout, where high temperatures combined with low humidity were linked to roughly double the odds of pain (odds ratio 2.04).⁷

Why the belief holds so tightly

If the effect is this small, why does it feel so certain? In 1996 the physician Donald Redelmeier and the psychologist Amos Tversky followed 18 people with arthritis for more than a year and found no significant link between their pain and the weather conditions each of them blamed.⁸ In a second experiment, 97 college students shown random, unrelated sequences tended to see correlations in them anyway.⁸ The authors' conclusion was gentle: the belief may come partly from the very human habit of finding patterns where none exist.⁸

That habit has a lot to work with, because joint pain moves on its own. When researchers asked people with hand, hip and knee osteoarthritis to rate their pain roughly every two hours on a weekday, the lowest score of the day averaged 17.9 out of 100 and the highest 54.4, an average swing of 36.4 points within a single day.⁹ Knee and hip osteoarthritis showed wider swings than hand osteoarthritis.⁹

How much knee, hip and hand pain moves in one day

Average weekday pain scores (1 to 100) in 157 people with osteoarthritis, rated about every two hours

Lowest rating of the day17.9

Average rating35.3

Highest rating of the day54.4

Source: Allen et al., Osteoarthritis and Cartilage (2009)

Put a bad afternoon next to a grey sky and the mind joins them. The many bad afternoons under blue skies, and the comfortable wet ones, are easier to forget. Grey days may also change how we spend our time, more hours in a chair and fewer on our feet, though the smartphone study suggests that mood and activity alone do not explain its small weather effect.⁶

What it means for a changeable knee

None of this says the ache is imagined. The pain is real, and for some people humidity, wind and pressure may nudge it a little. What the research suggests is that the weather is a minor voice in a crowded room: pain moves a great deal within an ordinary day, while the forecast's measurable share, in the best studies, is small.

That is, in its way, good news, since the weather is the one thing nobody can change. Ferreira's advice was to focus instead on "things you can control in regards to managing pain and prevention."⁵

That is also why Veema works on mobility inside the home, where most of those ordinary hours are spent. Whether an exoskeleton can help people keep moving through the good days and the bad ones 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. University of Manchester, Cloudy with a Chance of Pain press release (2019): Dixon quotes on Hippocrates and 'around three quarters' believing weather affects pain; over 13,000 recruited in 2016 across all 124 UK postcode areas; on damp, windy, low-pressure days the chance of more pain around 20% higher than an average day, i.e. 5 in 100 rising to 6 in 100; rainfall not associated, temperature not associated when averaged across the population. This is the university's press release; the peer-reviewed paper is source 6.
2. Timmermans et al., BMC Musculoskeletal Disorders (2014): 67.2% of older adults with osteoarthritis in six European countries reported weather sensitivity; mean pain 4.1 versus 3.1 (0 to 10); women, anxious people and southern Europeans more likely weather sensitive.
3. Jena et al., BMJ (2017): 1,552,842 Medicare beneficiaries aged 65 and over, 11,673,392 outpatient visits 2008 to 2012; adjusted share of visits for joint or back pain 6.35% on rainy days versus 6.39% on non-rainy days, opposite to expected direction and not clinically meaningful.
4. Timmermans et al., The Journal of Rheumatology (2015): 810 participants aged 65 to 85 with knee, hand and/or hip osteoarthritis; two-week pain calendars at three time points; pain associated with daily average humidity, stronger in colder conditions; day-to-day weather changes not significantly associated.
5. The George Institute for Global Health, media release on Ferreira et al., Osteoarthritis and Cartilage (2016): Media release (11 January 2017), not the paper itself: around 350 people with knee osteoarthritis; weather when pain was first noticed compared with one week and one month earlier, Bureau of Meteorology data; no link between pain and weather; Ferreira quotes. Study: Ferreira et al., Osteoarthritis and Cartilage 2016, DOI 10.1016/j.joca.2016.07.016.
6. Dixon et al., npj Digital Medicine (2019): Daily data from 2,658 patients; 'significant yet modest relationships between pain and relative humidity, pressure and wind speed', remaining after accounting for mood and physical activity.
7. Ferreira et al., Seminars in Arthritis and Rheumatism (2024): 11 case-crossover studies, 15,315 participants, 28,010 events; no association between relative humidity, air pressure, temperature or precipitation and rheumatoid arthritis, knee pain or low back pain; gout: high temperature with low humidity associated with increased pain (OR 2.04, 95% CI 1.26 to 3.30).
8. Redelmeier and Tversky, PNAS (1996): 18 patients with arthritis followed for more than a year with no significant pain-weather association; 97 college students perceived correlations in uncorrelated sequences.
9. Allen et al., Osteoarthritis and Cartilage (2009): Hand (40), hip (32) and knee (85) osteoarthritis; ratings about every 2 hours on a 1 to 100 scale; weekday mean minimum, average and maximum pain 17.9, 35.3 and 54.4; mean within-day range 36.4; knee and hip wider range than hand.