(Ivanhoe Newswire) -- Women with the strongest quadriceps appear to be protected against the development of knee osteoarthritis (OA) symptoms, according to a new study. While thigh muscle strength does not predict the presence of knee OA uncovered in x-rays, it does predict incidence of painful or stiff knee OA.

The knee is the weight-bearing joint most commonly affected by osteoarthritis. The Centers for Disease Control and Prevention (CDC) estimate that 26.9 million adults are affected by OA, with 16 percent of those cases occurring in the knee. Approximately 18.7 percent of symptomatic knee OA patients are female and 13.5 percent are male. Total expenditures for treatment of arthritis were estimated at $32 billion in 2005.

Neil Segal, M.D., M.S., and colleagues at the University of Iowa Hospitals and Clinics followed 3,026 men and women ages 50-79 over a 30-month period in the Multicenter Knee Osteoarthritis Study (MOST) to assess whether knee extensor strength would predict OA that can be determined through X-ray or symptomatic knee OA. Of those enrolled, a total of 2,519 knees were included in the study of radiographic knee OA and 3,392 knees were evaluated for the combination of radiographic OA and symptoms of OA that include pain, aching or stiffness on most days of the month.

Participants were evaluated for thigh muscle strength using an isokinetic dynamometer, a device that measures the strength of different muscle groups. The balance of muscle strength between quadriceps and hamstrings (H:Q ratio) was used to assess weakness in the lower extremity musculature. Knees were x-rayed at the onset of the study and at the conclusion to determine the presence of OA. A telephone screen at the beginning and end of the study was conducted to establish if frequent pain, aching or stiffness was present in the knee.