Scientists are devising a way to monitor the progression of osteoarthritis - by listening to a patient's knee.
Knees emit noises at levels the human ear cannot detect
A University of Central Lancashire team hope to harness a technique called acoustic emission, used by engineers to detect unsafe buildings and bridges.
The aim is to develop a hand-held device for GPs to use to analyse the high-frequency noises emitted by knees.
It could help assess whether arthritis is worsening or responding to therapy.
During movement, people's knees emit sound at frequencies which are too high to be detected by the human ear.
Based on their work to date, the team believes that an arthritic knee will emit high-frequency wave patterns which differ from those generated by a healthy knee.
They believe it should be possible to detect this difference by using acoustic emission.
Lead researcher Professor John Goodacre said: "Knees are frequently affected by osteoarthritis, rheumatoid arthritis and other types of chronic arthritis.
"It is increasingly important that clinicians have access to safe, convenient and reliable tools for measuring accurately if a patient's arthritis is deteriorating or improving, and whether or not treatments are working.
"Ultrasound and MRI are both increasingly used but are expensive and not easily accessible to most GPs or satisfactory for routine, widespread use in clinical practice.
"We hope to produce a convenient, non-invasive portable tool for use by doctors and other health professionals in primary care and in hospital to objectively monitor arthritis and responses to treatment."
It is well-recognised that joints produce sound during normal movement.
If two surfaces are smooth and well-lubricated they slide smoothly and quietly against each other.
However, if surfaces are rough and poorly lubricated - as in an arthritic knee - they will move unevenly against each other, producing a high-frequency, scratching sound.
The team hope to analyse the high-frequency sound from joints by using wide-band acoustic sensors attached to a microphone on a patient's knee.
As the patient flexes and extends their knee, the sensors measure the sound frequency emitted by the knee.
The team will try to identify if the sounds made by the knee correlates with cartilage loss demonstrated by MRI.
Professor Goodacre said: "We've already obtained some very encouraging early results, and we believe that this work could revolutionise current practice in the way arthritis is measured and monitored."
A spokeswoman for the Arthritis Research Campaign, which is funding the project, said: "Harnessing sound technology, normally used to detect structural faults in buildings, to detect and monitor the progression of osteoarthritis is ingenious, and should provide a safe, convenient tool for GPs."