Purpose Periprosthetic fracture (PPF) is a devastating complication following primary total knee arthroplasty. Obesity is currently considered a risk factor for many complications in orthopaedics, but there is no evidence in literature about the relationship between obesity and PPF around the knee. The objective of this study was to determine whether obesity is associated with a higher incidence of PPF. Methods All patients diagnosed of a PPF around the knee from January 2010 to December 2013 were enrolled. Forty-nine PPF (47 women and 2 men) were included, and a total of 97 patients (80 women and 17 men) were randomly obtained as a control group. Body mass index (BMI) was obtained in both groups and classified as < 25 (normal), overweight (25-29.9), obese (30-34.9), very obese (35-39.9), or morbid obesity (a parts per thousand yen40). Both groups, were also divided into subpopulations depending on the age as follows: < 70, 70-75, 75-80 and a parts per thousand yen80. Statistical analysis was performed to determine any difference in BMI a parts per thousand yen30 kg/mA(2) distribution between groups. Results In the PPF group 61.22 % of the patients had a BMI over 30 kg/mA(2) and likewise 62.88 % of the patients in the control group. No association was found between obesity and a higher risk of PPF (p < 0.05). Conclusion As a conclusion, obesity (BMI a parts per thousand yen30 kg/mA(2)) does not have any clinical relationship with the appearance of a periprosthetic fracture around the knee (p < 0.05).