Researchers have found that although thigh muscle strength does not predict the occurrence of knee osteoarthritis uncovered in x-rays, it does predict incidence of painful or stiff knee osteoarthritis. Women with the strongest quadriceps muscles appeared to be protected against the development of knee osteoarthritis symptoms.
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 osteoarthritis with 16% (aged 45+ years) of those cases occurring in the knee. Approximately 18.7 % of symptomatic knee osteoarthritis patients are female and 13.5% are male.
Neil Segal and colleagues 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 incident radiographic (osteoarthritis that can be determined through X-ray) or symptomatic knee osteoarthritis. Of those enrolled, a total of 2,519 knees were included in the study of radiographic knee osteoarthritis and 3,392 knees were evaluated for the combination of radiographic osteoarthritis and symptoms of osteoarthritis 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. X-rays of the knees were taken at the onset of the study and the conclusion to determine the presence of osteoarthritis. 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. Data on height, weight (Body Mass Index-BMI), femoral neck bone mineral density (BMD), and physical activity status was also collected from participants.
By the conclusion of the study 48 of 680 men and 93 of 937 women developed osteoarthritis 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 osteoarthritis. “Our results showed thigh muscle strength was not a significant predictor of radiographic knee osteoarthritis,” concluded the authors. Women in the top third of peak knee extensor strength had a lower incidence of symptomatic knee osteoarthritis, while men with strong thigh muscles had only slightly better odds of developing osteoarthritis symptoms compared to men with weaker knee extensor strength. “The H:Q ratios were not predictive of symptomatic knee osteoarthritis in either men or women,” added researchers.
Researchers acknowledge there to be some limitation to the study by not including assessments of hip abductor strength. “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 osteoarthritis of the knee,” said Dr. Segal. “These findings suggest that targeted interventions to reduce risk for symptomatic knee osteoarthritis could be directed toward increasing knee extensor strength,” he added.
References:
1. Neil A. Segal, James C. Torner, David Felson, Jingbo Niu, Leena Sharma, Cora E. Lewis, Michael Nevitt. Effect of Thigh Strength on Incident Radiographic and Symptomatic Knee Osteoarthritis in a Longitudinal Cohort. Arthritis Care & Research; Published Online: August 27, 2009 (DOI 10.1002/art)
