La Trobe University researchers have discovered people with hip osteoarthritis suffer from shrinkage of a special group of deep gluteal muscle, graphically documenting this by MRI (magnetic resonance imaging) scans.
The study has just been published in Osteoarthritis and Cartilage, journal of the International Osteoarthritis Research Society.
The lead researchers are Dr Rodney Green, Associate Professor in Human Anatomy, and PhD student Anita Zacharias at the Bendigo Campus. Other researchers include, Tania Pizzari, Daniel English and Theo Kapakoulakis.
Reduced muscle strength
Dr Green says it is well-known that people with hip osteoarthritis have reduced muscle strength, but until this latest study there has been no clear evidence of physical muscle wastage.
Exercise is widely offered as the most effective treatment, yet surprisingly recent research has revealed no benefit for patients over a ‘sham’ program, he says.
‘We think this may be due to currently prescribed exercise programs not targeting the correct muscle segments.’
The study was carried out in association with Bendigo Health and participants from the Bendigo community.
Muscle wastage and infiltrating fat
Dr Green says the hip is stabilised by various muscles, particularly the gluteus medius and gluteus minimus.
‘Our laboratory previously established that two of these fan-shaped gluteal stabilisermuscles (gluteus medius and minimus) are composed of functionally unique muscle segments.’
Using MRI, the latest study discovered a reduction in size of these two muscle groups in the limb of hip osteoarthritis patients when compared to the opposite limb and also when compared to people with normal hips.
‘And this reduction was associated with the severity of osteoarthritis, Dr Green says. ‘We also found increased levels of fatty infiltration in these muscles which occupied the spaces where the muscle had degenerated.’
Better rehabilitation program
Dr Green says EMG (electromyography) analysis is now underway to identify specific segments of these muscle groups that have altered function.
‘Once these have been identified we hope to create better rehabilitation programs targeting these specific segments of muscle – rather than the muscle as a whole – that could help improve overall joint function,’ Dr Green says.
Osteoarthritis affects about a quarter of all women and 16% of men over the age of 55. In Australia more than 18,000 hip replacement operations are carried out every year.
‘The condition is increasing with an ageing population, higher levels of obesity and sedentary lifestyle,’ Dr Green says.
‘Therefore, this is high priority research to help prevent and manage osteoarthritis.’
(Source: La Trobe University, Osteoarthritis and Cartilage)