The study led by researchers at the Universities of Oxford, University College Dublin and supported by The University of Manchester has recruited almost 3,000 patients so far.
But the team are still on the hunt for 2,000 more patients with psoriasis, a condition that causes flaky patches of skin covered with white scales which affects about 3% of people in the UK and Europe.
The 25% figure results confirms existing knowledge that up to a third will go on to develop psoriatic arthritis (PsA), which causes joints and tendons to become inflamed and painful.
Professor Laura Coates, Associate Professor at the University of Oxford, is leading the project. She said: 'At the moment there is no way to predict which patients with psoriasis are likely to go on to develop joint problems.
'This research will help us to design ways to prevent people with psoriasis developing arthritis, by offering potential drug treatments or lifestyle interventions such as exercise or stress management.'
Called the HIPPOCRATES Prospective Observational Study (HPOS), the online study monitors people with psoriasis over a three-year period to see who develops PsA.
Participants fill in questionnaires online and send small fingerprick blood samples by prepaid post.
After launching in the UK in July 2023 the study opened for recruitment in Ireland in August 2023 followed by Greece in February 2024 and Portugal in April 2024.
The study team in Oxford are working to open HPOS in a further 12 European countries with the ultimate goal to recruit 25,000 people with psoriasis.
Professor Coates added: 'This week on 19 and 20 June, researchers from across Europe will be meeting in Manchester to discuss the progress in the study so far.
'To date, we have baseline data on a total of 2,841 patients, of which 1761 are from Ireland and 1067 are from the UK.'
Professor Ann Barton from The University of Manchester will be leading on analysis of genetic samples collected in the study.
She said: 'We know that some patients with psoriasis will go on to develop psoriatic arthritis. If we could identify which patients are at higher risk for arthritis development, it could mean that in the future, those people could receive preventative treatment.
'Manchester is leading the work to identify genetic changes that could be used to predict which patients with psoriasis might be at increased risk of developing psoriatic arthritis. The HPOS study will allow us to collect samples from patients with psoriasis to help drive forward this work.'
Jayne Moggridge, who lives in Banbury, Oxfordshire had mild psoriasis on her scalp for a few years but recently went on to develop PsA.
Initially diagnosed as Complex Regional Pain Syndrome (CRPS) Jayne found herself in excruciating pain all the time. 'I was walking with a funny limp and when I was in a flare up I had to use a stick as well,' she said. 'But after I saw a new doctor at the Nuffield Orthopaedic Hospital my condition was diagnosed as psoriatic arthritis (PsA).'
After receiving her diagnosis Jayne's treatment plan changed and she saw some respite from the pain. But another bad flare up affected her feet, joints and tendons and made it hard to walk, so she was given another steroid injection to help with the pain.
An earlier diagnosis and treatment would have helped Jayne who said she would encourage everyone to take part in the HPOS study. 'In my case first I had fairly mild psoriasis, then I started to get muscle aches and it just got worse from there. If the condition was caught sooner and treatment started earlier, maybe there would have been a difference in how bad it got.'