Introduction: High body mass index (BMI) has been implicated as an etiologic agent in Achilles tendonitis (AT) and may contribute to poorer treatment outcomes. The purpose of this study was to better elucidate the role of BMI in both the development and treatment of AT.
Methods: A matched case-control (1:1) study design was used. Matching criteria were age, gender, and year of presentation. Consecutive patients who presented with a diagnosis of AT between 2002 and 2011 at a single foot and ankle specialty clinic were identified. Patients who presented with other foot pain at the same clinic served as controls (CG). The AT group was further stratified into treatment responders and nonresponders. The main effect measure for both analyses was an adjusted odds ratio.
Results: A total of 944 patients (472 AT; 472 CG) were included. AT patients had higher BMI than those in the CG (30.2 ± 6.5 vs 25.9 ± 5.3, P < .001). Overweight and obese patients were 2.6 to 6.6 times more likely than those with a normal BMI to present with Achilles tendonitis (P < .001). There was also elevated risk of presenting with AT at higher BMI categories (Mantel-Haenszel χ (2) = 8.074, P = .004). However, only age, not BMI, correlated with having failed conservative treatment among the AT group, with patients older than 65 years at the greatest risk (odds ratio = 2.4, 95% confidence interval = 1.5 to 4.1, P < .001).
Conclusion: BMI plays a role in the development of AT but does not appear to influence patient response to conservative treatment.
Levels of evidence: Prognostic, Level II.
Keywords: Achilles tendinosis; Achilles tendonitis; body mass index; extracorporeal shockwave therapy.