Morbid Obesity Is Associated With Fear of Movement and Lower Quality of Life in Patients With Knee Pain-Related Diagnoses

Abstract

To compare fear of movement in patients with different body mass index (BMI) values referred for rehabilitative care of the knee and to examine whether this fear contributed to self-reported knee-related function. We hypothesized that fear of movement would be elevated with increasing BMI and that fear would correspond with lower self-report knee-related function and lower quality of life (QOL). Retrospective cross-sectional study. Outpatient therapy clinic affiliated with a tertiary care hospital. Patients with knee pain diagnoses (n = 278) were stratified into 4 BMI groups (in < or =25 kg/m(2) nonobese; 25-29.9 kg/m(2) overweight; 30-39.9 kg/m(2) obese; > or =40 kg/m(2) morbidly obese). The Tampa Scale of Kinesiophobia (TSK; fear of movement), International Knee Documentation (IKDC; knee function), and Short-Form 8 (SF-8; QOL) scores were main outcomes. Pain and straight leg raise test scores also were collected. After review of the medical records, descriptive statistics and nonparametric tests were performed, and TSK, QOL, and SF-8 scores were compared. Hierarchical regression modeling determined the contribution of TSK scores to the variance of IKDC scores. Pain scores were greatest in the nonobese group and lowest in the morbidly obese group (7.5 +/- 2.6 points vs 4.8 +/- 3.1 points; P < .05). TSK scores in morbidly obese patients were greater than in nonobese patients (27.1 +/- 7.7 points vs 22.0 +/- 6.6 points; P = .002). The SF-8 mental-physical subscores were 27% to 32% lower in the morbidly obese than nonobese patients (both P < .0001). IKDC scores were lower in the morbidly obese than nonobese patients (32.1 +/- 19.2 points vs 50.9 +/- 23.8 points; P = .0001). Pain severity and TSK scores contributed 28.6% and 7.1% to the variance of the IKDC scores (overall R(2) = 68.6). Morbid obesity is associated with elevated fear of movement. Pain was the strongest predictor of IKDC scores, and fear of movement enhanced this predictive value of the regression model. Despite lower absolute pain severity in the morbidly obese group, this fear may influence IKDC scores in this population. Morbidly obese patients might benefit from rehabilitation activities that reduce fear of movement to optimize participation in rehabilitation activity.