OBJECTIVETo investigate the relationship between body mass index and lower limb alignment of patients with knee osteoarthritis.

METHODSFrom July 2008 to June 2010, 78 patients who suffered from severe knee osteoarthritis were treated with total knee replacement, including 17 males and 61 females, ranging from 41 to 85 years old, with an average age of 68.1 years. The Chinese average adult body mass index (BMI) classification standard was used to classify the patients into three groups: normal group, BMI<24.0, including 3 males and 11 females, totalized 14 patients (28 knees), with the mean age of (69.5 +/- 4.7); overweight group, 24.0 < or = BMI<28.0, including 4 males and 25 females, totalized 29 patients (58 knees), with the mean age of (66.4 +/- 7.9) years; and obese group, BMI > or = 28.0, including 10 males and 25 females, totalized 35 patients(70 knees), with the mean age of (69.1 +/- 8.3) years. The limb X-ray film measuring system was used to measure the lower limb alignment at the supine and weight-bearing position.

RESULTSThere were no statistical significances between the normal group and the overweight group in the knee varus angle at the supine and weight-bearing position (P>0.05). However, keen varus angle of the overweight group increased compared with the other two groups at the supine position,and the angle of the weight-bearing position increased nearly 2 degrees, but no statistical significance. There was no statistical significance between supine and weight-bearing position in the three groups of BMI, but the knee varus angle at the supine position was more than the weight -bearing position in the three groups.

CONCLUSIONThe knee varus angle of obese patients with osteoarthritis in the weight-bearing position increases obviously. It indicates that obesity is an important factor increasing the angle of lower limb alignment.