Orthopedic study suggests knee extensor strength plays a part in keeping osteoarthritis at bay

Orthopaedics Today

1^st on the web (August 27, 2009)

Researchers exploring factors that affect the risk of developing symptomatic knee osteoarthritis in a multicenter study found that women with the strongest thigh muscles developed the condition less often than women with weaker knee extensor strength.

According to findings from the Multicenter Knee Osteoarthritis Study, funded by the U.S. National Institute on Aging, men with stronger thigh muscles were only slightly more protected from developing symptomatic OA than those with weaker muscles. Furthermore, thigh muscle strength was not helpful for predicting radiographic OA in women or men, the investigators noted in their study, which appears online today in Arthritis Care & Research.

“These findings suggest that targeted interventions to reduce risk for symptomatic knee OA could be directed toward increasing knee extensor strength,” co-investigator Neal A. Segal, MD, MS, from the department of orthopedics and rehabilitation at the University of Iowa, said in a press release.

Segal and colleagues studied the knees of 3,026 men and women 50 to 79 years old. They measured study participants’ thigh muscle strength with a dynamometer and determined their H:Q ratio, an indication of the balance of strength between hamstrings and quadriceps.

Investigators followed subjects 30 months using knee radiographs and telephone interviews to establish baseline OA, pain and other knee symptoms with the goal of determining whether knee extensor strength was a predictor of radiographic or symptomatic knee OA.

To draw their conclusions, they took into account the participants’ height, weight, body mass index, femoral neck bone mineral density and self-assessed level of physical activity.

At the end of their study, investigators reported that 7.1 % of men and 9.9% of women developed radiographic knee OA, compared to 7.8% of men and 10.1% of women who had signs of symptomatic OA. “H:Q ratio was not predictive of symptomatic knee OA in either men or women,” they wrote in their results.

The lack of hip abductor strength assessments in the analysis was one of the study limitations, the researchers noted in the press release.

“Study of hip abductor strength, which is important for control of the knee joint, may be useful in a more comprehensive study of risk for OA of the knee,” Segal said in the release.

Reference:

• Segal NA, Torner JC, Felson D, et al. Effect of thigh strength on incident radiographic and symptomatic knee osteoarthritis in a longitudinal cohort. Arthritis Care Res. Published online Aug. 27, 2009 (DOI 10.1002/art).