Investigation of foot posture disorders and related factors in patients with fibromyalgia

Objective: The aim of this study is to evaluate foot posture abnormalities and potentially related parameters (joint hypermobility, mechanical properties of extrinsic foot muscles, clinical variables, etc.) in patients with fibromyalgia. Materials and Methods: Fibromyalgia patients and age- and gender-matched healthy adults were included in the study. Static foot posture was assessed using the Foot Posture Index (FPI), joint hypermobility and benign joint hypermobility syndrome were evaluated using the Beighton and Brighton criteria. Mechanical properties of gastrocnemius medialis, tibialis anterior, and peroneus longus were examined by the MyotonPRO® device (Myoton AS, Tallinn, Estonia). Foot function, quality of life, and physical activity level were assessed using the Foot Function Index (FFI), Short Form36 (SF-36), and International Physical Activity Questionnaire Short Form (IPAQShort), respectively. Functionality and clinical impact level of fibromyalgia patients were evaluated using the Fibromyalgia Impact Questionnaire. Results: The study included 86 patients with fibromyalgia and 41 adults as a control group. Foot posture abnormalities were observed more frequently in the fibromyalgia group than those in the control group (p=0.006). Pronation foot posture was observed in most of the patients (61.6 %). Pronation foot posture was detected in 85.5% of those with joint hypermobility and in 87.1% of those meeting BJHS criteria. Patients with joint hypermobility/BJHS were found to have lower body weight, body mass index (BMI), and higher Symptom Severity Scale (SSS) score and regular exercise habits. The elasticity of the peroneus longus muscle at rest and the elasticity of the tibialis anterior muscle in the standing position were significantly different between the fibromyalgia patients and the control group (p = 0.037 and p = 0.011, respectively). No difference was detected among the foot posture groups of the patients in terms of myotonometric data. Conclusion: Pronation foot posture disorder is common in fibromyalgia. The frequency of this foot posture disorder is even higher in fibromyalgia patients with joint hypermobility and/or BJHS. Keywords: fibromyalgia, foot, tonus, stiffness, elasticity.