Determinant factors of pain intensity in overweight and obese adults with knee osteoarthritis.

Osteoarthritis is one of the most disabling diseases, the main symptom being pain, which is associated with a low level of physical activity. The incidence and progression of knee osteoarthritis are directly related with risk factors such as obesity, age and mechanical factors. OBJECTIVE: The aim of this study was to identify which variables (physical activity, anthropometry and body composition of the lower limb) best predict pain intensity in obese individuals with knee osteoarthritis. METHODS: The sample consisted of 44 individuals of both genders (mean age 56.6 ± 6.6 yrs). Anthropometric measures of body mass, stature, mid-thigh, patellar and calf circumferences, and foot breadth were obtained. The body composition of the most painful lower limb was obtained by dual-energy X-ray absorptiometry in different regions: mid-thigh; patella; calf and foot. For each of these regions, fat mass percentage, the amount of fat and fat-free mass, bone mass and bone mineral density were evaluated. Physical activity was assessed by the International Physical Activity Questionnaire (short version) and pain intensity with the numeric rating scale. Data analysis was done using the multifactorial logistic regression (backward conditional method). RESULTS: The multifactorial analysis showed that gender (Odds Ratio of 7.448 for a 95% Confidence Interval of [1.032 – 53.747]) and foot breadth (Odds Ratio of 3.730 for a 95% Confidence Interval of [1.006 – 13.827]) are important factors to explain the risk of pain. CONCLUSIONS: These results seem to indicate that the assessment of foot morphology must be considered in knee osteoarthritis studies, since foot breadth is a predictor of knee pain. Further research is required to investigate the influence of foot morphology as well as of the use of insoles, splints or adapting shoes, on obese individuals with knee osteoarthritis.