This study will compare the thickness of the plantar fascia in stretched and relaxed positions in patients with plantar fasciopathy using ultrasonography.

The purpose of this observational study is to compare the thickness of the plantar fascia in stretched and relaxed positions of the most symptomatic heel in patients with plantar fasciopathy using ultrasonography.

In addition to this, we will compare measurements of the thickness of the plantar fascia in sagittal versus transversal transducer positions, compare pressure pain thresholds at the most tender spot of the plantar fascia in stretched and relaxed position using pressure algometry and investigate the association between the thickness of the plantar fascia and the pressure pain threshold. All measurements are performed bilaterally starting with the most symptomatic foot.

To compare thickness and pressure pain thresholds in stretched and relaxed positions of the plantar fascia paired-t-tests are used. To compare the most and least symptomatic sides paired-t-tests will be used.

The association between the thickness of the plantar fascia and pressure pain threshold will be investigated using the Pearson's correlation coefficient.

Inclusion Criteria:

• History of plantar heel pain of at least 3 months
• Clinical presentation of pain and/or tenderness to palpation in the area of the medial tubercle of the calcaneus
• Average intensity of pain in the previous week equal to or greater than 3 on an 11-point visual analog scale (VAS)
• Thickness of symptomatic plantar fascia of 4 mm or greater

Exclusion Criteria:

• Age under 18
• Pregnancy
• History of systemic disease with manifestations similar to those of plantar fasciopathy
• Pain medication in the last 24 hours
• Steroid injection for plantar fasciopathy in the previous 6 months
• Previous heel surgery or fracture of the lower leg or foot

The study will include patients from the local community of the municipality of Aalborg, Denmark.