Study: Knee OA cannot be predicted, but strong thigh muscles are good prevention

IOWA CITY, Iowa A new study by researchers at the University of Iowa Hospitals and Clinics found that thigh muscle strength does not predict the occurrence of knee osteoarthritis uncovered in x-rays, but does predict incidence of painful or stiff knee OA. Women with the strongest quadriceps muscles appeared to be protected against the development of knee OA symptoms, according to the study published in the September issue of Arthritis Care & Research, a journal published by Wiley-Blackwell on behalf of the American College of Rheumatology.

The knee is the most common weight-bearing joint affected by osteoarthritis or degenerative joint disease, a major cause of disability in the U.S. The Centers for Disease Control and Prevention estimate that 26.9 million U.S. adults are affected by OA with 16% (aged 45+ years) of those cases occurring in the knee. Approximately 18.7% of symptomatic knee OA patients are female and 13.5% are male. A Medical Expenditure Panel Survey estimates that total out-of-pocket expenditures for treatment of arthritis was $32 billion in 2005.

Neil Segal and colleagues in a study funded by the National Institute on Aging followed 3,026 men and women ages 50-79 over a 30-month period in the Multicenter Knee Osteoarthritis Study to assess whether knee extensor strength would predict incident radiographic (OA that can be determined through X-ray) or symptomatic knee OA.

By the conclusion of the study 48 of 680 men and 93 of 937 women developed OA detected by x-ray. At the end of the 30-month period 10.1% of women and 7.8% of men displayed signs of symptomatic knee OA. “Our results showed thigh muscle strength was not a significant predictor of radiographic knee OA,” concluded the authors. Women in the top third of peak knee extensor strength had a lower incidence of symptomatic knee OA, while men with strong thigh muscles had only slightly better odds of developing OA symptoms compared to men with weaker knee extensor strength. “The H:Q ratios were not predictive of symptomatic knee OA in either men or women,” added researchers.

“These findings suggest that targeted interventions to reduce risk for symptomatic knee OA could be directed toward increasing knee extensor strength,” Segal said.