Purpose

The purpose of this study were to investigate whether there is an association between the preoperative body mass index in total knee replacement patients and the effect three to five years postoperative.

Background: In Denmark there is every year performed 5000 total knee Arthroplasty, and the number increase fast every year. The most common indication for total knee Arthroplasty is arthrosis which constitute 80 %. Convincing studies shows that overweight and obesity are the most important reason for develop arthrosis. On the contrary the relationship between overweight and outcome are ambiguous. This study examinant whether there is association between body mass index and the clinical outcome at 1 year following primary total knee Arthroplasty.

Method and material: A total of 158 patients, 116 woman and 42 men undergoing a total knee Arthroplasty replacement from the hospital of southern Jutland Sonderborg in the period January 1. 2005 – December 31. 2006. Each patient where followed from the day of the surgery to 1 year postoperative. There were four clinical outcome measures; functional score, knee score, functional score improvement and knee score improvement. Data was collected from medical records and the database Dansk Knæalloplastik Register.

Results: In woman there were found significant negative linear relationship between body mass index and knee score improvement – 0.97 (p=0.003). The correlations coefficient for body mass index and knee score was significant (p=0.04). There were significant associations between body mass index and all four outcome measures for patients > 65 years; functional score (p= 0.006), knee score (p=0.01), functional score improvement – 1.09 (p=0.017) and knee score improvement – 1.14 (p=0.006). For the patients < 65 years there was a positively significant linear relationship between body mass index and functional score improvement 1.47 (p=0.01). In the functional score there was not found significant relationship whit body mass index in this age group (p=0.12).

Conclusion: This study shows evidence for overweight and obesity in patients undergone a total knee Arthroplasty has implications for how much the patient achieves clinical improvement after 1 year postoperative. The higher body mass index the patient has, the worse score obtained.