Differences In Foot Characteristics Between The Involved And Uninvolved Sides In People With Plantar Fasciitis

BACKGROUND: Individuals with plantar fasciitis exhibit increased plantar fascia (PF) thickness, decreased PF stiffness, reduced intrinsic muscle strength, and lower arch heights compared to healthy controls. However, comparison between all of these variables have not been examined in the involved and uninvolved feet of people with unilateral plantar fasciitis at the same study. PURPOSE: To examine differences between, and relationships among, plantar fascia stiffness thickness, intrinsic foot muscle strength, and arch height index between limbs in individuals with unilateral PF. METHODS: This is an ongoing study where 8 individuals (52.33 ± 7.70 yrs., 7 F and 1 M) with unilateral plantar fasciitis have been recruited to date. The PF stiffness and thickness (measured with ultrasound), intrinsic foot muscle strength (measured with a dynamometer) and arch height index (measured with calipers) were compared between involved and uninvolved feet. Given the limited sample size, relative changes (%) and effect sizes were used for comparison. Correlations between the variables were also computed. RESULTS: The involved foot exhibited 13% lower PF stiffness, and 18% greater PF thickness. Additionally, doming and hallux strength were 13% and 15% lower respectively in the involved foot. All the other differences were small. CONCLUSION: We note that reduced stiffness and increased thickness of the PF as well as weakness of doming and hallux strength in the involved feet. There were no differences in arch height index variables between involved and uninvolved feet. The statistical confirmation of these results will become more robust as additional subjects are added to the dataset. Research reported in this abstract was supported by the National Institute for Aging of the National Institutes of Health under award number R01AG071646. - Uninjured(Mean ± SD) Injured (Mean ± SD) Changes % Effect size PF thickness (cm) 0.29 ± 0.04 0.35 ± 0.01 18 .57 PF stiffness (kPa) 230.27 ± 51.04 202.27 ± 39.33 13 .62 Doming strength (N) 100.32 ± 38.64 88.33 ± 26.44 13 .36 Hallux Strength (N) 68.32 ± 29.29 59.32 ± 25.28 15 .34 2-5 toes Strength (N) 58.84 ± 23.44 55.91 ± 20.55 5 .13 AHI Seated (AHI unit) 0.33 ± 0.6 0.33 ± 0.06 1 .05 AHI Standing (AHI unit) 0.30 ± 0.5 0.30 ± 0.06 1 .05 AHI Stiffness (kg/AHI unit) 2109.37 ± 1491.80 1854.37 ± 1219.52 13 .23 Key: AHI: Arch height index, SD = Standard deviation Research reported in this abstract was supported by the National Institute for Aging of the National Institutes of Health under award number R01AG071646.