Thigh Muscle Specific‐Strength and the Risk of Incident Knee Osteoarthritis: The Influence of Sex and Greater Body Mass Index

• Published in: Arthritis care & research (2010) Vol. 69; no. 8; pp. 1266 - 1270
• Main Authors: Culvenor, Adam G., Felson, David T., Niu, Jingbo, Wirth, Wolfgang, Sattler, Martina, Dannhauer, Torben, Eckstein, Felix
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.08.2017
• Subjects: Aged; Arthritis; Body mass; Body Mass Index; Female; Follow-Up Studies; Humans; Incidence; Knee; Longitudinal Studies; Magnetic resonance imaging; Male; Middle Aged; Muscle contraction; Muscle strength; Muscle Strength - physiology; Osteoarthritis; Osteoarthritis, Knee - diagnostic imaging; Osteoarthritis, Knee - epidemiology; Osteoarthritis, Knee - physiopathology; Quadriceps Muscle - diagnostic imaging; Quadriceps Muscle - physiology; Risk Factors; Sex Factors; Thigh - diagnostic imaging; Thigh - physiology
• ISSN: 2151-464X; 2151-4658
• DOI: 10.1002/acr.23182

Objective To determine whether lower thigh muscle specific‐strength increases the risk of incident radiographic knee osteoarthritis (RKOA), and whether there exists a sex‐specific relationship between thigh muscle specific‐strength and body mass index (BMI). Methods A total of 161 Osteoarthritis Initiative participants (62% female) with incident RKOA (Kellgren/Lawrence grade 0/1 at baseline, developing an osteophyte and joint space narrowing grade ≥1 by year 4) were matched to 186 controls (58% female) without incident RKOA. Thigh muscle anatomical cross‐sectional areas (ACSAs) were determined at baseline using axial magnetic resonance imaging scans. Isometric extensor and flexor muscle strength was measured at baseline, and specific strength (strength ÷ ACSA) was calculated. Logistic regression assessed the risk of incident RKOA associated with muscle specific‐strength (with and without adjustment for BMI). Results Lower knee extensor– and flexor–specific strength significantly increased the risk of incident RKOA in women but not in men (odds ratio 1.47 [95% confidence interval (95% CI) 1.10–1.96] and 1.41 [95% CI 1.06–1.89], respectively). The significant relationship in women was lost after adjustment for BMI. Lower specific strength was associated with higher BMI in women (r = −0.29, P < 0.001), but not in men, whereas absolute strength was associated with BMI in men (r = 0.28, P = 0.001), but not in women. Conclusion Lower thigh muscle specific‐strength predicts incident RKOA in women, with this relationship being confounded by BMI. The sex‐specific relationship between muscle specific‐strength and BMI provides a possible explanation why women with muscle‐strength deficits typically have a poorer prognosis than men with similar strength deficits.