Obesity in early adulthood predicts knee pain and walking difficulties among men: A life course study

Few studies have addressed the role of obesity in young adulthood in knee problems later in life. We assessed the associations of overweight/obesity with knee pain and functional limitations of the knee across the life course.

Military health records from 1967 to 2000 (baseline) were searched for 18- to 50-year-old Finnish men (n = 1913) who participated in the Health 2000 Study (follow-up). Visits to health care were followed during service. Height and weight were measured at baseline and follow-up and waist circumference at follow-up. Weight was inquired at follow-up for ages of 20, 30, 40 and 50 years, if applicable. Life course body mass index (BMI) was calculated. One-month knee pain and functional limitations (walking difficulties and limping) due to knee problems were enquired with interview at follow-up. Cox regression model, logistic regression and trajectory analysis were applied.

Body mass index at the age of 20 increased the risk of unilateral knee pain by 38% and functional limitations by 27% for one standard deviation increment of BMI, respectively. One-unit increment of Z-score of life course BMI increased knee pain by 32%. Development of severe obesity during the follow-up increased the risk of knee pain by 80% and functional limitations by 93%. The effect of obesity on functional limitations was partly mediated by traumatic knee problems during military service.

Reducing overweight already in adolescence and avoiding further weight gain during life course may prevent knee pain and associated disability. WHAT DOES THIS STUDY ADD?: BMI at the age of 20 increases the likelihood of knee pain and functional limitations of the knee later in life. Development of severe obesity in adulthood increases the risk of knee pain by 80% and functional limitations by more than 90%. Both general and abdominal obesity are associated with knee pain, associations being stronger for general obesity.