Leg length discrepancy is not a risk factor for plantar fasciitis

Purpose: Plantar fasciitis (PF) is a main source of heel pain, and only about one-third of patients have bilateral symptomatic involvement, although age, body mass index (BMI), and physical activities are known risk factors. The high prevalence of unilateral involvement is poorly understood. We aimed to assess the potential association between PF and the leg length discrepancy (LLD) in unilateral PF. Methods: A transversal case-control study was conducted from January 2019 to December 2020, including 120 participants allocated to two groups matched by BMI and sex: cases (with a diagnosis of PF; 50 +/- 13 years) and control (without foot pain; 40 +/- 15 years). For both groups, a difference greater than 0.64 cm in the scanometry determined the criteria for the presence of LLD. Results: The multivariate logistic regression analysis showed an independent association of PF only with age (p < 0.001), and no association with LLD. We did not observe differences in the mean discrepancy (1.37 +/- 0.83 cm in the PF group in comparison with 1.13 +/- 0.37 cm in the control group, [p > 0.05]) or in the prevalence of LLD between groups (48% [n = 29] in the PF group compared with 42% [n = 25] in the control group, [p > 0.05]). In the PF group, 80% of the participants reported unilateral pain. We observed a higher prevalence of pain in the shorter limb (p < 0.05). Conclusion: Age was the only factor associated with the diagnosis of PF when groups were matched by sex and BMI. LLD was not an independent factor associated with the diagnosis of PF. However, when PF is unilateral, the shorter limb is more affected with 70% of prevalence. Level of evidence: Level III, case-control.