Material properties of intrinsic foot structures in individuals with plantar fasciitis

The etiology of plantar fasciitis remains unclear, with diagnosis relying heavily on patient history. Knowledge of foot intrinsic material properties associated with this condition may improve our understanding of the etiology and treatment efforts for plantar fasciitis. The purpose of the present study is to assess longitudinal material stiffness of the plantar fascia (PF) and relevant foot structures supporting the longitudinal arch in individuals with and without plantar fasciitis.

Individuals with no history of plantar fasciitis (controls) (n = 11), with active plantar fasciitis symptoms (n = 11), and with history of plantar fasciitis symptoms (n = 6) underwent bilateral shear wave elastography (SWE) measurements of the PF, flexor hallucis brevis, abductor hallucis muscle and tendon, and Achilles tendon. Structure thickness was assessed using B-mode imaging. Clinical foot measures including navicular drop (cm), arch stiffness (N/cm), longitudinal arch angle, arch index, and gastrocnemius and soleus flexibility were also compared between groups.

PF longitudinal stiffness at a proximal site was significantly lower in individuals with active plantar fasciitis than those with a history of plantar fasciitis and controls. Longitudinal stiffness varied along PF length across groups. Both plantar fasciitis groups exhibited increased thickness along the PF compared to controls.

Decreased proximal PF stiffness was observed among symptomatic participants, while increased PF thickness was observed in both plantar fasciitis groups, and no differences between groups were observed in clinical foot measures. SWE may be useful to monitor recovery and treatment effectiveness, especially in the absence of clinical foot measures and/or PF thickness changes.