Reduced meniscal extrusion may be one of the mechanisms by which weight loss and exercise improve symptoms and function for people with knee osteoarthritis, Australian research suggests.

An MRI study of 106 patients involved in the IDEA (Intensive Diet and Exercise  for Arthritis) trial found that the degree of weight loss was significantly associated with reduced progression of medial meniscus extrusion over an 18 month period.

Presenting the findings at the 2019 OARSI World Congress on Osteoarthritis in Toronto, research student Ishanka Munugoda of the Menzies Institute for Medical Research, Tasmania, said the study involved obese patients with knee OA over the age of 55 who had a BMI in excess of 27kg/m2. MRI images were obtained at baseline and after 18 months of follow up.

Previously reported outcomes from the study showed that patients lost an average of 10% body weight, and this was associated with marked reductions in OA symptoms as well as mechanistic outcomes such as joint compressive force and markers of inflammation. However there was no apparent effect on rate of structural progression either on X-ray or MRI over 18-months.

But  a new analysis of MRI images showed that  weight loss was associated with  less longitudinal progression of medial meniscus extrusion as well as a decrease in maximum and mean medial meniscus extrusion distance of 18 months.

There were also consistent trends in the relationship between weight loss and meniscus area not covering tibial plateau, tibial coverage and overlap distance in the medial meniscus, consistent with those for extrusion, though these did not reach significance. Likewise similar changes in lateral meniscus and changes in meniscus size did not reach statistical significance, possibly due to the small trial size.

Nevertheless, the decrease in extrusion distance seen with weight loss added to other findings suggesting a role for meniscal extrusion and better clinical outcomes in knee OA, he said.

“Given the relationship between the quantitative  measures of meniscus extrusion and knee symptoms shown previously, the current data  indicate the meniscus extrusion may be one of the mechanisms by which weight loss translates into clinical benefit,” he concluded.