Weight loss reduces knee-joint loads in overweight and obese older adults with knee osteoarthritis.
OBJECTIVE
To determine the relationship between change in body mass and knee-joint moments and forces during walking in overweight and obese older adults with knee osteoarthritis (OA) following an 18-month clinical trial of diet and exercise.


METHODS
Data were obtained from 142 sedentary, overweight, and obese older adults with self-reported disability and radiographic evidence of knee OA who underwent 3-dimensional gait analysis. Gait kinetic outcome variables included peak knee-joint forces and peak internal knee-joint moments. Mixed regression models were created to predict followup kinetic values, using followup body mass as the primary explanatory variable. Baseline body mass was used as a covariate, and thus followup body mass was a surrogate measure for change in body mass (i.e., weight loss).


RESULTS
There was a significant direct association between followup body mass and peak followup values of compressive force (P = 0.001), resultant force (P = 0.002), abduction moment (P = 0.03), and medial rotation moment (P = 0.02). A weight reduction of 9.8 N (1 kg) was associated with reductions of 40.6 N and 38.7 N in compressive and resultant forces, respectively. Thus, each weight-loss unit was associated with an approximately 4-unit reduction in knee-joint forces. In addition, a reduction in body weight of 9.8 N (1 kg) was associated with a 1.4% reduction (0.496 Nm) in knee abduction moment.


CONCLUSIONS
Our results indicate that each pound of weight lost will result in a 4-fold reduction in the load exerted on the knee per step during daily activities. Accumulated over thousands of steps per day, a reduction of this magnitude would appear to be clinically meaningful.
Snow Biomechanics Laboratory, Department of Health and Exercise Science, Wake Forest University, Winston-Salem, North Carolina 27109, USA. messier@wfu.edu
Stephen P
SP
Messier
David J
DJ
Gutekunst
Cralen
C
Davis
Paul
P
DeVita
D000368:Aged; D000369:Aged, 80 and over; D001835:Body Weight; D004035:Diet Therapy; D005081:Exercise Therapy; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications / Q000503:physiopathology / Q000628:therapy*; D020370:Osteoarthritis, Knee / Q000150:complications / Q000503:physiopathology / Q000628:therapy*; D016037:Single-Blind Method; D016896:Treatment Outcome; D015431:Weight Loss; D016474:Weight-Bearing