BIOMECHANICAL IMPACT OF BODY MASS INDEX ON KNEE JOINT LOADING, FUNCTION, AND EARLY OSTEOARTHRITIC CHANGES IN ADULTS

Body Mass Index (BMI) is an important factor influencing knee biomechanics, pain, and functional performance, yet its early impact in young adults remains insufficiently understood. This study aimed to examine the biomechanical impact of BMI on knee joint function, pain, stair-climbing performance, and lower limb alignment in young adults. A cross- sectional observational study was conducted among 54 participants recruited through convenience sampling. Data were collected using a structured proforma including anthropometric measures, the International Knee Documentation Committee (IKDC) score, Numeric Pain Rating Scale (NPRS), Stair Climb Test, and lower limb alignment assessment. Statistical analysis included descriptive statistics, Pearson correlation, simple and multiple regression, and two-way ANOVA, with significance set at p < 0.05. The mean BMI was 22.18 ± 3.63 kg/m², mean NPRS score was 5.28 ± 2.13, and mean IKDC score was 65.23 ± 12.72. BMI did not significantly predict IKDC score (F (1,52) = 0.665, p = 0.419; R² = 0.013), but it showed a strong positive correlation with Stair Climb Test time (r = 0.856, p < 0.01) and Risk Score (r = 0.742, p < 0.01). Multiple regression showed BMI as the only significant predictor of stair performance (B = 0.779, β = 0.860, p < 0.001), explaining 74.2% of variance (R² = 0.742). Two-way ANOVA showed significant effects of BMI category (p = 0.026), alignment (p = 0.003), and their interaction (p = 0.035) on IKDC score. In conclusion, BMI was strongly associated with poorer functional performance and higher biomechanical risk, while lower limb alignment significantly influenced knee function. Early BMI screening, functional assessment, weight management, strengthening, and alignment-focused physiotherapy are recommended to reduce future knee osteoarthritis risk in young adults.